Specific Heat.-If we mix a kilogramme of water at 80 C. with a kilogramme at 40° C., we shall obtain a mixture of two kilogrammes of The specific heat of ice is 0.504, water 1, water, the temperature of which would be 60° C.; steam 04805; it is therefore seen that water and, again, if we inix 50 cbc. of water at 0° C. is an exception to the above rule. Tur- the number is 22:47, which is nearer 23 than 46, with 50 cbc. at 100° C. we shall obtain about pentine has a specific heat of 0.4259, whilst that so it is classed as a monad, and 23 adopted as its 100 cbc. at 50° C., the temperature being the of its vapour is 0.5061. The following are atomic weight. arithmetical mean of the mixture. But if we the specific heats of some of the most important make a mixture of two dissimilar substances, bodies:

THE INSPECTION OF BOILERS.

knowledge and the most versatile abilities, distinguished alike as scholar, poet, physician, and naturalist; who just 202 years ago gave to the world the idea which it is my purpose to trace. He did not trouble himself with speculative considerations, but attacked experimentally what had been considered to be particular cases of spontaneof meat," he said; "I expose them to the air in hot ous generation. "Here are dead animals, or pieces weather, and in a few days they swarm with magdead flesh; but if I put similar bodies, while quite gots. You tell me that these are generated in the

and certified, at least once a year, as safe and trustworthy. Instead, however, of entrusting the duty of carrying out these inspections, and granting the certificates to the Board of Trade, or to the town councils, or other local authorities, or to certified boiler makers, private inspection associations, or insurance companies, they propose that there should be formed a National Steam Users' Board, and that this board should be empowered to carry out the system of inspection required, including the granting certificates, fixing the rate of charge for each boiler, &c. The board to be an honorary and representative body, about is to say, millowners or others-using boilers for merwere respectively due to faults of construction cantile purposes; and the remainder to be men of and faults of working. Considering the facilities science that is to say, engineers and others-comwe now have for testing the strength of boilers petent to advise on matters relating to the inspection and their capabilities for doing the work required of boilers, and to add weight to the conncils of the of them, this state of things must be considered board. This system would throw no administrative deplorable. When a boiler explodes after due responsibility on the Government, and would secure inspection, there is some reason or excuse in saythe integrity and efficiency of the inspections. Thus the steam users would be left to govern theming that it was an accident; but when an explo-selves, a responsibility with which it is thought they sion takes place with a boiler that has never been might be entrusted, since they have a strong desire to examined, and probably received but careless avoid Governmental interference, and they would know attention, surely a verdict of manslaughter should that unless they succeeded the Government would take be returned in the event of any one being killed. the matter into its own hands. The committee conThe majority of the steam users in their evi-sider this plan calculated to guard the inspections dence before the Parliamentary Committee, whose or arbitrary and oppressive on the other. against being lax and contradictory on the one hand, sittings are adjourned till next session, were of opinion that inspection should be made compulsory by an Act of Parliament; but they were unanimous in refusing a Government examination. It was urged that all boilers should be registered and receive a certificate that they are in working order, which would be of assistance in case of accident, but should certainly not relieve the owner of his responsibility. The hydraulic test is cheap, easy, and efficient, and if this, or some test equally reliable, is not adopted, no matter what may be the actual cause of explosion, surely an "accident" must be considered the result of culpable negligence.

S from time to time we receive the reports of the various boiler inspection and assurance companies, the necessity for some compulsory examination recurs with renewed force. From the report of Mr. Marten, the chief engineer of the Midland Steam Boiler Inspection and Assurance Company, we find that records have been obtained of thirty-seven explosions this year. Of these, no fewer than thirteen were due to 'culpable negligence," whilst seven and fourteen one-half of its members being men of commerce-that fresh, into a jar, and tie some fine gauze over the

insurance.

top of the jar, not a maggot makes its appearance, while the dead substances, nevertheless, putrefy just in the same way as before. It is obvious, therefore, that the maggots are not generated by the corruption of the meat; and that the cause of their formation must be something which is kept away by gauze. But gauze will not keep away aeriform bodies or fluids. This something must, therefore, exist in the form of solid particles too big to get through the gauze. Nor is one long left in doubt what these solid particles are; for the blow-flies, attracted by the odour of the meat, swarm round the vessel, and, urged by a powerful, but in this case misleading instinct, lay eggs, ont of which maggots are immediately hatched upon the gauze. The conclusion, therefore, is unavoidable, -the maggots are not generated by the meat, but the eggs which give rise to them are brought through the air by the flies."

Almost childishly simple as these experiments now seem, they were at that time new; and they are worthy of careful study. Every piece of experimental work since done in relation to this subject has been shaped upon the model left by the Italian philosopher. And as Redi's results were the same, however varied the nature of the materials he used, it is not wonderful that there arose in his mind a prelife from dead matter the real explanation was the sumption that in all cases of seeming production of introduction of living germs from without into that dead matter. It became necessary that this hypothesis should in every case be considered and refuted before the production of life in any other way could be admitted by careful reasoners. The hypothesis will be mentioned so frequently that, to save cirgenesis; and Ishall term the contrary doctrine,-th: t cumlocution, I shall call it the hypothesis of Bio

On considering the proposition to inflict a penalty in case of explosion, it appears by no means clear that it would have the effect of inducing all steam users to enrol their boilers. The next question is as to the value of the inspections by competing joint-stock insurance companies. Inspection costs much more than office better to allow boilers to blow up and pay comConsequently it will pay an insurance pensation, than to prevent explosions and pay for inspection. The charge for insurance rises according to the pressure of steam. The committee decidedly incline to the plan of enforcing inspection directly by withont apprehensions that however ingeniously the law rather than indirectly by penalty. They are not principle of joint-stock insurance might be surrounded with a series of checks and counter-checks, yet that it A boiler can be inspected at so moderate a rate would lead to inspection being cut down to the lowest that any neglect of this precaution should be possible point. On the other hand, were the inspection punished, in the event of an explosion, with enforced by law, and nationally administered either by severe measures. We are not of opinion that a central steam board or by a series of district ones, Government interference is desirable; but if users be secured. With the additional experience of another they consider that a far more generous system would of steam persist in neglecting ordinary precau-year, they feel compelled to take one other step in ad-living matter may be produced by not living matter tions we see no alternative but to make the vance, and they have come to the conclusion that the the hypothesis of Abiogenesis. It is interesting periodical inspection of boilers compulsory, and time has arrived when the Government should enforce to hold the employer responsible for damages to life or limb. All the Government interference that is necessary consists in permitting no boiler to be worked that is not certified as being in good order by a properly qualified officer of one of the associations now in existence or to be formed.

the periodical inspection of all steam boilers. They
are convinced that explosions might be, and ought to
for this purpose, and that any well organized system of
be, prevented; the competent inspection is adequate
inspection extended throughout the entire country
would practically extinguish boiler explosions.

Sir William Fairbairn thinks there should be an
inspection of boilers every three months, and that
every man who had a boiler should submit it to a
careful inspection.

to observe that Redi did not escape the customary tax upon a discoverer, of having to defend himse f the Scriptures; for his adversaries declared that the against the charge of impugning the authority of generation of bees out of the carcass of a dead lion is affirmed in the book of Judges to have been the origin of the riddle with which Samson perplexed the Philistines. Against all odds, however, the philosopher did splendid battle in the cause of Biogenesis; but he held the doctrine in a sense which, him to be classed among the defenders of "sponif he had lived in these times, would have caused taneous generation."

This, together with holding the user responsible for any damage that may result from an explosion, both civilly and criminally, will do much to alleviate the distressing consequences of an incautious and careless use of steam. That 16 persons should be killed and 27 injured in 8 months by explosions due solely to carelessness, is a state of things that calls for immediate and effectual action. The committee appointed to inquire into this subject by the British Association have pre- was strongly opposed, however, to any Government in- admitted that he had not sufficient evidence to bear

sented their report to the Mechanical Science Section.

The committee consisted of Sir William Fairbairn, Sir Joseph Whitworth, Messrs. John Penn, J. Bramwell, Hugh Mason, Rigby, Schofield, P. Beyer, Webster, Q.C., and Lavington E. Fletcher, and reports that the frequent occurrence of steamboiler explosion, with the loss of life and property caused thereby, was called attention to last year, at Exeter, and in a paper read the year before that, at Norwich. Those sad catastrophes still continue with unabated frequency. In the interval between the Norwich and Exeter meetings 46 explosions occurred, killing 78 persons and injuring 114 others. Since then 57 more explosions have occurred, killing 99 more persons and injuring 96 others. Boilers burst simply from weakness, that weakness arising in some cases from original malconstruction, in others from defeetive condition consequent on wear and tear, and in others again from neglect of attendants through allowing the plates over the furnace to become overheated from shortness of water, &c. Competent inspection is adequate to detect the weakness of the boiler in time to prevent explosions, whether that weakness arise from malconstruction or defective condition, while it tends to stimulate attendants to carefuluess, and thus to diminish the number of those explosions arising from oversight. The two leading causes of the explosions were malconstruction and defective condition, a small proportion being due only to the neglect of the attendants. It may be put shortly, that for every explosion due to the boiler minder through neglecting the water supply, &c., six are due to the boiler maker or boiler owner, through making or using bad boilers. It is clear, therefore, that the adoption of competent inspection by every boiler owner in the kingdom would do much to prevent the constant recurrence of boiler explosions, and to save the greater part of the 75 lives annually sacrificed. The committee recommend that inspection should be compulsory and that Parliament should enact that no boiler should be worked unless periodically inspected

many accidents to the dishonest construction of
The President (Mr. C. B. Vignolles) attributes
boilers. Our English habits seemed to kick against
anything like Government interference, but such acci-
dents as had arisen from boiler explosions should be
put an end to as forcibly as possible-like stamping out
valgar prejudices-if necessary, by an iron hand. He
the smallpox or the cattle plague, notwithstanding

spection, which was a mere formality-a mere farce.
The Government should pass a law making the inspec-
tion of boilers compulsory.

Omne ricum ex viro, aphoristically sums up his doctrine, but he went no further. He had specnlatively anticipated the manner in which grubs are deposited in fruits and in the galls of plants, but he

that they are generated by a modification of the
him out, and he therefore preferred the supposition
living substance of the plants themselves. Indeed,
he regarded these vegetable growths as organs by
which a plant gives rise to an animal, and he looked
upon this production of animals as the final cause
explain in the same way the production of parasites
HE following is the substance of the Address to apprehend Redi's position rightly; for naturalists
within the animal body. It is of great importance
Tdelivered by Professor Huxley, as President of posworking upon the lines of
the British Association for the Advancement of thought he laid down. Clearly he held Biogenesis
Science, at the meeting held at Liverpool, Sep- as against Abiogenesis, and I shall immediately pro-
tember, 1870. After a few introductory remarks, ceed to inquire how far subsequent investigations
the Professor said :-
have borne him out in so doing. But Redi also
thought that there were two modes of Biogenesis.
By one, of common occurrence, the parent gives
rise to offspring, which passes through the same
cycle of changes as itself, and this has been termed
Homogenesis. By the other, the parent was sup-
posed to give rise to offspring which passed through
à different series of states, and did not return into
the cycle of the parent. This ought to be called
permanently unlike the parent.
Heterogenesis, the offspring being altogether and
The term, how-
Milne-Edwards has substituted for it Xenogenesis,
ever, has been used in another sense, and M.
which means the generation of something foreign.

PROFESSOR HUXLEY ON THE THEORY OF of galls and of some fruits. He proposed, also, to
SPONTANEOUS GENERATION.

It is a matter of everyday experience that it is
difficult to prevent many articles of food from
becoming covered with monld; that fruit, sound
enough to all appearance, often contains grubs at
the core; that meat, left to itself in the air, is apt
to putrefy and swarm with maggots. Even ordi-
nary water, if allowed to stand in an open vessel,
sooner or later becomes turbid and full of living
matter.
terrogated as to the cause of these phenomena,
The philosophers of antiquity, when in-
It did not enter their minds even to doubt that
were provided with a ready and plausible answer.
these low forms of life were generated in the mat-
ters in which they made their appearance, and the
proposition that life may, and does proceed from
that which has no life, was held alike by the philo-
sophers, the poets, and the people of the most
enlightened nations 1,800 years ago, and remained
the accepted doctrine of learned and unlearned
Europe, through the Middle Ages down even to the
seventeenth century.

The first repudiation of it, the first distinct enun-
ciation of the proposition that all living matter has
sprung from pre-existing living matter, came from
an Italian, Francesco Redi, a man of the widest

After discussing Redi's hypothesis of universal Biogenesis, I shall go on to ask how far the growth of science justifies his other hypothesis of Xenogenesis. The progress of Biogenesis was triumphant and unchecked for nearly a century. The earlier applications of the microscope to anatomy revealed such a complexity of organization in the lowest forms of life and such a prodigality of provision for their multiplication, that the hypothesis of Abiogenesis began to appear not only untrue but absurd, and, in the middle of the 18th century, when Button and Needham took up the question, it was almost

universally discredited. But the skill of the micro-covery of Cagniard de la Tour, that common yeast
scope makers of that day soon reached its limits, is composed of a vast accumulation of minute plants.
and an enlargement of 400 diameters, which was Thus fermentation, in so far as it is attended by
the most to which they attained, is barely sufficient the development of microscopical organisms in
to display as mere dots and lines a large proportion enormous numbers, became assimilated to the de-
of the minute active creatures known as infusorial composition of an ordinary infusion; and it was an
animalcules, which swarm in water containing any obvious suggestion that the organisms were, in
animal or vegetable body. Led by various theoretical some way or other, the causes both of fermenta-
considerations, Buffon and Needham doubted the tion and of putrefaction. The chemists, headed by
applicability of Redi's hypothesis to the infusorial Berzelius and Liebig, laughed the notion to scorn;
animalcules, and Needham endeavoured to bring the but in 1843 it was shown by the since illustrious
question to an experimental test. He argued that Helmholtz that the interposition of a membrane
if these creatures were produced from germs, the between a putrefying of a fermenting liquid and one
germs must exist either in the substance infused, or that was simply putrescible or fermentible pre-
in the water, or in the superjacent air.
vented the formation of organisms in the latter.
Therefore, the cause of the development of these
organisms must be something that cannot pass
through membrane; and, when viewed by the
light of Graham's subsequent researches upon
colloids, Helmholtz's experiments narrowed the
issue to this: that which excites fermentation and
putrefaction, and at the same time gives rise to
living forms in an infusion, is not a gas, and is
not a diffusible fluid; therefore it is either a colloid,
or it is matter divided into very minute solid
particles.

Now the vitality of germs is destroyed by heat; and
hence, if the infusion were boiled, carefully corked,
and the vessels containing it again heated, all germs
present would be destroyed. Consequently, on
Redi's hypothesis, when the vessels thus prepared
were set aside to cool, no animalcules should be de-
veloped in them, whereas if animalcules are not
dependent upon pre-existing germs, but are generated
from the substance infused, they ought in time to
make their appearance. Needham found, under the
circumstances in which he made his experiments,
that animalcules always did arise in the infusions. The investigations of Schroeder and Dusch in
In much of his work Needham was associated with 1854, and of Schroeder alone in 1859, cleared up this
Buffon, and the results of their experiments fitted point by showing that the exclusion of air from an
with the French naturalist's hypothesis of organic infusion by a plug of cotton wool prevented patre-
molecules," according to which life is the inde- faction, fermentation, and the development of
feasible property of certain indestructible molecules organic forms. It is hard to imagine what the fine
of matter which exist in all living things, and have sieve formed by cotton wool could have excluded,
inherent activities by which they are distinguished excepting minute solid particles, but it was reserved
from not living matter. Each individual living for Professor Tyndall to complete the demonstration
organism is formed by their temporary combination.-first, by showing that ordinary air does contain
They stand to it in the relation of the particles of such particles, and secondly, that filtration through
water to a cascade or a whirlpool, or to a mould into cotton wool removes them. It has been a common ob-
which the water is poured. The form of the organ- jection to the doctrine of Biogenesis that if it were
ism is thus determined by the reaction between ex- true the air must be thick with germs; and the
ternal conditions and the inherent activities of the Abiogenists regard this as the height of absurdity.
organic molecules of which it is composed; and as Professor Tyndall has proved that ordinary air is
the stoppage of a whirlpool destroys nothing but a no better than a stirabout of excessively minute
form, and leaves the molecules of the water with all solid particles; that these particles are almost
their inherent activities intact, so what we call the wholly destructible by heat; and that they are
death and putrefaction of an animal or of a plant is strained off, and the air rendered optically pure, by
merely the breaking up of the form, or manner of passing through a layer of cotton wool. It remains
association, of its constituent organic molecules, yet in the order of logic, though not of history, to
which are then set free as infusorial animalcules. show that among these solid destructible particles
It will be perceived that this doctrine is by no there are germs capable of giving rise to living
means identical with Abiogenesis, with which it is forms. This was done by M. Pasteur, in those
often confounded. On this hypothesis, a piece of beautiful researches which will ever render his name
beef, or a handful of hay, is dead only in a limited famous, and which, in spite of all attacks upon
sense. The beef is dead ox, and the hay is dead them, appear to me to be models of accurate experi-
grass; but the "organic molecules" of the beef or mentation and logical reasoning.
the hay are not dead, but are ready to manifest
their vitality as soon as the bovine or herbaceous
shrouds in which they are imprisoned are rent by
the macerating action of water. The hypothesis,
therefore, must be classified under Xenogenesis
rather than under Abiogenesis. Such as it was, I
think it will appear, to those who will be just
enough to remember that it was propounded before
the birth of modern chemistry and of the modern
optical arts, to be a most ingenious and suggestive
speculation.

But the great tragedy of science-the slaying of a beautiful hypothesis by an ugly fact-which is so constantly being enacted under the eyes of philosophers, was played almost immediately, for the benefit of Buffon and Needham. The Abbé Spallanzani suggested that Needham's experiments had not been conducted with sufficient care; and showed that a more prolonged exposure of the flasks to an elevated temperature, and a more complete method of closing them, entirely prevented the appearance of animalcules. But we all too often forget that it is one thing to refute a proposition, and another to prove the truth of a doctrine that contradicts that proposition; and the advance of science soon showed that though Needham might be quite wrong, it did not follow that Spallanzani was quite right. The discovery of oxygen, and of some of its relations to the phenomena of life, opened a new aspect to the question, and occasioned doubts as to what might have happened to the organic matter of the infusions, or to the oxygen of the air, in Spallanzani's experiments. What security was there that the development of life had not been checked or prevented by chemical changes?

It was needful to repeat the experiments under conditions which would make sure that neither the oxygen of the air nor the composition of the organic matter was altered in such a manner as to interfere with the existence of life. Schulze and Schwann devised means of accomplishing this, by causing the only air which reached the infusions to pass through red-hot tubes or through strong sulphuric acid. They found that an infusion so treated developed no living things; but that if it was afterwards exposed to common air life appeared abundantly. The accuracy of their experiments has been by turns affirmed and denied, but, in any case, they only proved that the treatment to which the air had been subjected had destroyed something that was essential to the development of life in infusions. This something might be solid, fluid, or gaseous; that it consisted of germs remained only an hypothesis, of more or less probability. Contemporaneously with these investigations came the dis

From the whole chain of evidence it is demonstrable:-That a fluid eminently fit for the develop ment of the lowest forms of life, but which contains neither germs nor any protean compound, gives rise to living things in great abundance, if it is exposed to ordinary air; while no such development takes place if the air with which it is in contact is mechanically freed from the solid particles which ordinarily float in it, and which may be made visible by appropriate means. It is demonstrable that the great majority of these particles are destructible by heat, and that some of them are germs, or living particles, capable of giving rise to the same forms of life as those which appear when the fluid is exposed to unpurified air. It is demonstrable that inoculation of the experimental fluid with a drop of liquid known to contain living particles gives rise to the same phenomena as exposure to unpurified air. And it is further certain that these living particles are so minute that the assumption of their suspension in ordinary air presents not the slightest difficulty. On the contrary, considering their lightness and the wide diffusion of the organisms which produce them, it is impossible to conceive that they should not be suspended in the atmosphere in myriads.

Thus, the evidence, direct and indirect, in favour of Biogenesis for all known forms of life must, I think, he admitted to be of great weight. On the other side, the sole assertions worthy of attention are, that hermetically-sealed fluids, which have been exposed to great and long-continued heat, have sometimes exhibited living forms of low organization when they have been opened. The first reply that suggests itself is the probability that there must be some error about these experiments, because they are performed on an enormous scale every day with quite contrary results. Meat, fruits, vegetables, the very materials of the most fermentable and putrescible infusions are preserved to the extent, I suppose I may say, of thousands of tons every year, by a method which is a mere application of Spallanzani's experiment. The matters to be preserved are well boiled in a tin case provided with a small hole, and this hole is soldered up when all the air in the case has been replaced by steam. By this method they may be kept for years without putrefying, fermenting, or getting mouldy. Now this is not because oxygen is excluded, inasmuch as it is now proved that free oxygen is not necessary for either fermentation or putrefaction. It is not because the tins are exhausted of air, for Vibriones and Bacteria live, as Pasteur has shown, without air or free oxygen. It is not because the boiled meats or vegetables are not putrescible or

fermentable, as those who have had the misfor tune to be in a ship supplied with unskillfully closed tins well know. What is it, therefore, but the exclusion of germs? I think that Abiogenists are bound to answer this question before they ask us to consider new experiments of precisely the same order. And in the next place, if the results of the experiments I refer to are really trustworthy, it by no means follows that Abiogenesis has taken place. The resistance of living matter to heat is known to vary within considerable limits, and to depend to some extent upon the chemical and physical qualities of the surrounding medium. But if, in the present state of science, the alternative is offered us-either germs can stand a greater heat than has been supposed, or the molecules of dead matter, for no valid or intelligible reason that is assigned, are able to re-arrange themselves into living bodies, exactly such as can be demonstrated to be frequently produced in another way, I cannot understand how choice can be, even for a moment, doubtful.

But though I cannot express this conviction of mine too strongly, I must carefully guard myself against the supposition that I intend to suggest that no such thing as Abiogenesis ever has taken place in the past, or ever will take place in the future. With organic chemistry, molecular physics, and physiology yet in their infancy, and every day making prodigious strides, I think it would be the height of presumption for any man to say that the conditions under which matter assumes the properties we call "vital" may not, some day, be artificially brought together. All I feel justified in affirming is, that I see no reason for believing that the feat has been performed yet. And, looking back through the prodigious vista of the past, I find no record of the commencement of life, and therefore I am devoid of any means of forming a definite conclusion as to the conditions of its appearance. Belief, in the scientific sense of the word, is a serious matter, and needs strong foundations. To say, therefore, in the admitted absence of evidence, that I have any belief as to the mode in which the existing forms of life have originated, would be using words in a wrong sense. But expectation is permissible where belief is not; and if it were given me to look beyond the abyss of geologically recorded time, to the still more remote period when the earth was passing through physical and chemical conditions which it can no more see again than a man can recall his infancy, I should expect to be a witness of the evolution of living protoplasm from not living matter. I should expect to see it appear under forms of great simplicity, endowed, like exist. ing Fungi, with the power of determining the formation of new protoplasm from such matters as ammonium carbonates, oxalates and tartrates, alkaline and earthy phosphates, and water, without the aid of light. That is the expectation to which analogical reasoning leads me; but I beg you once more to recollect that I have no right to call my opinion anything but an act of philosophical faith. So much for the history of the progress of Redi's great doctrine of Biogenesis, which appears to me, with the limitations I have expressed, to be victorious along the whole line at the present day.

As regards the second problem offered to us by Redi, whether Xenogenesis obtains, side by side with Homogenesis; whether, that is, there exist not only the ordinary living things, giving rise to offspring which run through the same cycle as themselves, but also others, producing offspring which are of a totally different character from themselves, the researches of two centuries have led to a different result. That the grubs found in galls are no product of the plants on which the galls grow, but are the result of the introduction of the eggs of insects into the substance of these plants, was made out by Vallisnieri, Réaumur, and others, before the end of the first half of the eighteenth century. The tapeworms, bladderworms, and flukes continued to be a stronghold of the advocates of Xenogenesis for a much longer period. Indeed, it is only within the last thirty years that the splendid patience of Von Siebold, Van Beneden, Leuckart, Kuchenmeister, other helminthologists, has succeeded in tracing every such parasite, often through the strangest wanderings and metamorphoses, to an egg derived from a parent, actually or potentially like itself; and the tendency of inquiries elsewhere has all been in the same direction. A plant may throw off bulbs, but these, sooner or later, give rise to seeds or spores, which develop into the original form. A polype may give rise to Medusa, or a pluteus to an Echinoderm, but the Medusa and the Echinoderm give rise to eggs which produce polypes or plutei, and they are, therefore, only stages in the cycle of life of the species.

and

But if we turn to pathology it offers us some remarkable approximations to true Xenogenesis. As I have already mentioned, it has been known since the time of Vallisnieri and of Réaumur, that galls in plants, and tumours of cattle, are caused by insects, which lay their eggs in those parts of the animal or vegetable frame of which these morbid structures are ontgrowths. Again, it is a matter of familiar experience to everybody that mere pressure on the skin will give rise to a corn.

Now, the gall, the tumour, and the corn are parts of the living body, which have become to a certain degree independent and distinct organisms. Under the influence of certain external conditions, elements of the body, which should have developed in due subordination to its general plan, set up for themselves and apply the nourishment which they receive to their own purposes. innocent productions as corns and warts, there are From such all gradations to the serious tumours, which, by their mere size and the mechanical obstruction they cause, destroy the organism out of which they are developed; while, finally, in those terrible structures, known as cancers, the abnormal growth has acquired powers of reproduction and multiplication, and is only morphologically distinguish able from the parasitic worm, the life of which is neither more nor less closely bound up with that of the infested organism.

66

If there were a kind of diseased structure, the histological elements of which were capable of maintaining a separate and independent existence out of the body, it seems to me that the shadowy boundary between morbid growth and Xenogenesis would be effaced. And I am inclined to think that the progress of discovery has almost brought us to this point already. I have been favoured by Mr. Simon with an early copy of the last published of the valuable which, in his capacity of their medical officer, he Reports on the Public Health," annually presents to the Lords of the Privy Council. The appendix to this report contains an introductory essay "On the Intimate Pathology of Contagion," by Dr. Burdon Sanderson, which is one of the clearest, most comprehensive, and well-reasoned discussions of a great question which has come under my notice for a long time. I refer you to it for details and for the authorities for the statements I am about to make. You are familiar with what happens in vaccination. made in the skin, and an infinitesimal quantity of A minute cut is vaccine matter is inserted into the wound. Within a certain time a vesicle appears in the place of the wound, and the fluid which distends this vesicle is vaccine matter, in quantity a hundred or a thousand fold that which was originally inserted. Now what has taken place in the course of this operation? Has the vaccine matter by its irritative property produced a mere blister, the fluid of which has the same irritative property? matter contain living particles which have grown Or does the vaccine and multiplied where they have been planted? The observations of M. Chauveau, extended and confirmed by Dr. Sanderson himself, appear to leave no doubt upon this head. Experiments, similar in principle to those of Helmholtz on fermentation and putrefaction, have proved that the active element in the vaccine lymph is non-diffusible, and consists of minute particles not exceeding 1-20,000in. in diameter, which are made visible in the lymph by the microscope. Similar experiments have proved that two of the most destructive of epizootic diseases, sheep-pox and glanders, are also dependent for their existence and their propagation upon extremely small living solid particles, to which the title of "microzymes " is applied. An animal suffering under either of these terrible diseases is a source of infection and contagion to others, for precisely the same reason that a tub of fermenting beer is capable of propagating its fermentation by "infection 66 or contagion both cases it is the solid living particles which are to fresh wort. In efficient; the liquid in which they float, and at the expense of which they live, being altogether passive.

Now arises the question, Are these microzymes the results of Homogenesis, or of Xenogenesis? are they capable, like the Torule of yeast, of arising only by the development of pre-existing germs; or may they be, like the constituents of a nut-gall, the results of a modification and individualization of the tissues of the body in which they are found, resulting from the operation of certain conditions? Are they parasites in the zoological sense, or are they merely what Virchow has called "heterologous growth"? It is obvious that this question has the most profound importance, whether we look at it from a practical or from a theoretical point of view. A parasite may be stamped out by destroying its germs, but a pathological product can only be annihilated by removing the conditions which give rise to it. It appears to me that this great problem will have to be solved for each zymotic disease se parately, for analogy cuts two ways. upon the analogy of pathological modification, I have dwelt which is in favour of the xenogenetic origin of microzymes; but I must now speak of the equally strong analogies in favour of the origin of such pestiferous particles by the ordinary process of the

generation of like from like.

It is, at present, a well-established fact that certain diseases, both of plants and of animals, which have all the characters of contagious and infectious epidemics, are caused by minute organisms. The smut of wheat is a well-known instance of such a disease, and it cannot be doubted that the grape disease and the potato disease fall under the same category. Among animals, insects are wonderfully liable to the ravages of contagious and infectious diseases caused by microscopic fungi. In autumn, it is not

9

uncommon to see flies motionless upon a window- this strange disease a multitude of cylindrical pane, with a sort of magic circle, in white, drawn corpuscles, each about 1-6000th of an inch long. round them. magic circle was found to consist of innumerable named by him Panhistophyton; for the reason that, spores, which have been thrown off in all directions in subjects in which the disease is strongly deOn microscopic examination, the These have been carefully studied by Lebert, and by a minute fungus called Empusa musca, the veloped, the corpuscles swarm in every tissue and spore-forming filaments of which stand out like a organ of the body, and even pass into the unspore-forming filaments are connected with others, corpuscles causes, or mere concomitants, of the pile of velvet from the body of the fly. which fill the interior of the fly's body with so much disease? Some naturalists took one view and some fine wool, having eaten away and destroyed the another; and it was not until the French GovernThese developed eggs of the female moth. But are these creature's viscera. This is the full-grown condition ment, alarmed by the continued ravages of the of the Empusa. stages, in flies which are still active, and to all had been suggested, despatched M. Pasteur to study appearance healthy, it is found to exist in the form it, that the question received its final settlement; If traced back to its earlier malady, and the inefficiency of the remedies which of minute corpuscles, which float in the blood of at a great sacrifice, not only of the time and peace the fly. These multiply and lengthen into filaments of mind of that eminent philosopher, but, I regret at the expense of the fly's substance: and when they to have to add, of his health. body and give off spores. Healthy flies shut up have at last killed the patient, they grow out of its with diseased ones catch this mortal disease and perish like the others.

the development of the Empusa in the fly very
A most competent observer, M. Cohn, who studied
carefully, was utterly unable to discover in what
manner the smallest germs of the Empusa got into
the fly. The spores could not be made to give rise
to such germs by cultivation, nor were such germs
looked exceedingly like a case of Abiogenesis, or, at
discoverable in the air, or in the food of the fly. It
any rate, of Xenogenesis; and it is only quite
recently that the real course of events has been
made out.
of the spores falls upon the body of a fly it begins
to germinate, and sends out a process which bores
It has been ascertained that when one
its way through the fly's skin; this, having reached
the interior cavities of its body, gives off the minute
floating corpuscles which are the earliest stage of
the Empusa. The disease is "contagious," because
from which the spore-bearing filaments protrude, is
a healthy fly coming in contact with a diseased one,
pretty sure to carry off a spore or two.
infectious," because the spores become scattered
about all sorts of matter in the neighbourhood of
It is
the slain flies.

to a very fatal, contagious, and infectious disease,
The silkworm has long been known to be subject
called the Muscardine. Audouin transmitted it by
inoculation.
body of the caterpillar; and its contagiousness and
development of a fungus, Botrytis Bassiana, in the
This disease is entirely due to the
infectiousness are accounted for in the same way
still more serious epizootic has appeared among the
as those of the fly disease. But of late years a
silkworms; and I may mention a few facts which
will give you some conception of the gravity of the
injury which it has inflicted on France alone. The
production of silk has been for centuries an impor-
tant branch of industry in Southern France, and in
the year 1853 it had attained such a magnitude,
that the annual produce of the French sericulture
was estimated to amount to a tenth of that of the
whole world, and represented a money value of
117,000,000 of francs, or about £5,000,000 sterling.
What may be the sum which would represent the
money value of all the industries connected with
the working up of the raw silk thus produced is
more than I can pretend to estimate. Suffice it to
say that the city of Lyons is built upon French silk
as much as Manchester was upon American cotton
diseases; and even before 1853 a peculiar epizootic,
before the civil war.
frequently accompanied by the appearance of dark
Silkworms are liable to many
spots upon the skin (whence the name of "Pébrine
tality. But in the years following 1853 this malady
which it has received), had been noted for its mor-
broke out with such extreme violence that in 1856
the silk crop was reduced to a third of the amount
which it had reached in 1853; and up to within the
last year or two it has never attained half the yield
of 1853. This means not only that the great number
of people engaged in silk-growing are some thirty
millions sterling poorer than they might have been;
it means not only that high prices have had to be
paid for imported silkworm eggs, and that, after
investing his money in them, in paying for mul-
berry-leaves and for attendance, the cultivator has
constantly seen his silkworms perish and himself
plunged in ruin; but it means that the looms of
Lyons have lacked employment, and that for years
enforced idleness and misery have been the portion
of a vast population which in former days was in-
dustrious and well-to-do.

French Academy of Sciences to appoint com-
In 1858 the gravity of the situation caused the
missioners of whom a distinguished naturalist,
M. de Quatrefages, was one-to inquire into the
nature of this disease, and, if possible, to devise
some means of staying the plague. In reading the
ceedingly interesting to observe that his elaborate
study of the Pebrine forced the conviction upon his
report made by M. de Quatrefages in 1859, it is ex-
mind that, in its mode of occurrence and propaga-
tion, the disease of the silkworm is, in every respect,
comparable to the cholera among mankind. But it
differs from the cholera, and, so far, is a more for-
midable disease, in being hereditary, and in being,
under some circumstances, contagious, as well as
infectious.
covered in the blood of the silkworms affected by
The Italian naturalist, Filippi, dis-

certain that this devastating, cholera-like Pebrine is the effect of the growth and multiplication of the But the sacrifice has not been in vain. It is now Panhistophyton pass away from the bodies of the and infectious because the corpuscles of the deceased caterpillars, directly or indirectly, to the Panhistophyton in the silkworm. It is contagious alimentary canal of healthy silkworms in their neighbourhood; it is hereditary, because the corpuscles enter into the eggs while they are being when they are laid; and for this reason, also, it formed, and consequently are carried within them presents the very singular peculiarity of being inherited only on the mother's side. There is not a accountable phenomena presented by the Pébrine, but has received its explanation from the fact that single one of all the apparently capricious and unthe disease is the result of the presence of the microscopic organism, Panhistophyton.

what are the indications as to the method of preway in which the Panhistophyton is generated. venting it? It is obvious that this depends upon the Such being the facts with respect to Pébrine, Xenogenesis, within the silkworm or its moth, the extirpation of the disease must depend upon the If it may be generated by Abiogenesis, or by on the other hand, the Panhistophyton is an inunder which this generation takes place. But if, dependent organism, which is no more generated prevention of the occurrence of the conditions though it may need the silkworm for its developthe oak, or the apple-tree, on which it grows, by the silkworm than the mistletoe is generated by ment in the same way as the mistletoe needs The sole thing to be done is to get rid of and keep the tree, then the indications are totally different. away the germs of the Panhistophyton. As might be imagined from the course of his previous investigations, M. Pasteur was led to believe that the latter was the right theory; and guided by that theory, he has devised a method of extirpating the disease, which has proved to be completely successful wherever it has been properly carried out.

among insects, contagious and infectious diseases, of great malignity, are caused by minute organisms which are produced from pre-existing There can be no reason, then, for doubting that, germs, or by Homogenesis; and there is no reason, that I know of, for believing that what happens in insects may not take place in the highest animals. Indeed, there is already strong evidence that some diseases of an extremely malignant and fatal chawork of minute organisms as in the Pebrine. I refer for this evidence to the very striking facts racter to which man is subject, are as much the treatment. It seems to me impossible to rise from known publications on the antiseptic method of the perusal of these publications without a strong adduced by Professor Lister in his various wellconviction that the lamentable mortality which so frequently dogs the footsteps of the most skilful operator, and those deadly consequences of wounds and injuries which seem to haunt the very walls of great hospitals, and are, even now, destroying more men than die of bullet or bayonet, are due to the importation of minute organisms into wounds, and their increase and multiplication; and that the surgeon who saves most lives will be he who best works out the practical consequences of the hypothesis of Redi.

me in an attempt to trace the path which has been
followed by a scientific idea, in its long and slow
progress from the position of a probable hypothesis
I commenced this address by asking you to follow
has lain chiefly in a land flowing with the abomin-
has not taken us into very attractive regions; it
to that of an established law of nature. Our survey
able, and peopled with mere grubs and mouldiness.
And it may be imagined with what smiles and shrugs
practical and serious contemporaries of Redi and of
Spallanzani may have commented on the waste of
problems which, though curious enough in them-
selves, could be of no conceivable utility to man-
their high abilities in toiling at the solution of
kind. Nevertheless, you will have observed, that
before we had travelled very far upon our road there
appeared, on the right and on the left, fields laden
with a harvest of golden grain, immediately con-
vertible into those things which the most sordidly
practical of men will admit to have value-namely,
by the Pébrine in seventeen years cannot be esti-
money and life. The direct loss to France caused

mated at less than fifty millions sterling; and if we add to this what Redi's idea, in Pasteur's hands, has done for the wine-grower and for the vinegar maker, and try to capitalize its value, we shall find that it will go a long way towards repairing the money losses caused by the frightful and calamitous war of this autumn.

And as to the equivalent of Redi's thought in life, how can we over-estimate the value of that knowledge of the nature of epidemic and epizootic diseases, and consequently of the means of checking or eradicating them, the dawn of which has assuredly commenced? Looking back no further than ten years, it is possible to select three (1863, 1864, and 1869) in which the total number of deaths from scarlet fever alone amounted to 90,000. That is the return of the killed-the maimed and disabled

ON THE PRESENT STATE OF THE QUES.
TION RELATIVE TO LUNAR ACTIVITY OR
QUIESCENCE.

as a disinfecting agent; as a varnish for leather, | selenographers just named; also that no change of and for many other useful purposes. There are a physical character has taken place in it during very few bodies that can attack or in any way de- the 3 years it has been under constant observation. compose paraffine, and hence its great value in It has been supposed that photography would many chemical processes. Its use is likely to be solve all such difficulties, and that photograms of further extended the more we become familiar with the lunar surface taken under similar angles of illnits properties, and it appears destined to assume an mination and visual ray would agree with each important position among chemical industries. other; but here, again, precisely the same difficulties present themselves which perplexed Schröter, and which have been met with in comparing Lohrmann's and Beer and Madler's works. Objects figured by the earlier selenographers occur on some photograms, but not on others, of about the same phases of illumination. There appears to be an agency capable of affecting the visibility of objects, rendering them indistinct or invisible on Some taken place in the crater Linne producing phenooccasions, while on others they are distinctly seen on the photograms. Whatever operations may have mena―the recurrence of which is rare in all the examples above mentioned, from Schröter's time to character, exceedingly difficult of explanation, and the present-we have the phenomena of a different constituting an important element in the solution of the question of present activity or quiescence; depend upon changes of visual and illuminating more immediately connected with the moon itself. To effect such a proof, however, is a matter of no for the delineation of lunar features; and in the small difficulty. Mädler alludes to the performance of calculations of the most varied kind as necessary case before us the calculation of several elements for each separate observation-and they are very

BY W. R. BIRT, F.R.A.S. being left out of sight. Why, it is to be hoped that change on the moon's surface has been more ROM the tune of Schröter, the question of the list of killed in the present bloodiest of all wars or less agitated. The "Selenotopographische Frag will not amount to more than this. But the facts, mente which I have placed before you, must leave the contains numerous instances of what he least sanguine without a doubt that the nature and considered to be changes of a temporary character, the causes of this scourge will, one day, be as well formation of new craters. It is, however, notorious and a few of a more permanent nature, as the understood as those of the Pébrine are now; and that he failed to establish the fact of a decided that the long-suffered massacre of our innocents change in any one instance; nor is this to be wonwill come to an end. And thus mankind will have dered at when we consider the paucity of the for unless it be fully proved that all these instances one more admonition that "the people perish for materials he had at his command. Notwithstanding lack of knowledge; " and that the alleviation of the the comparative neglect into which the observations angles, a strong suspicion will exist of their being miseries and the promotion of the welfare of men recorded in the "Fragments" have fallen, and the must be sought by those who will not lose their pains in that diligent, patient, loving study of all judgments passed upon them by some of the best the multitudinous aspects of Nature, the result of that they embody the results of zealous and perse: known selenographers, there can be no question which constitute exact knowledge or science. It is vering attention to the moon's surface, and ought the justification and the glory of this great meeting not to be passed over in the examination of any that it is gathered together for no other object than given spot, the history of which we are desirous of the advancement of the moiety of science which becoming acquainted with, during the earliest period numerous-is absolutely essential for the purpose

deals with those phenomena of nature which we call physical. May its endeavours be crowned with

a full measure of success!

A$

THE NEW POSTAL REGULATIONS.

a

of referring the phenomena observed to changes of labours of his successors, Lohrmann, and Beer and kind have not yet been made to any great extent, of descriptive observational selenography. The illumination and visual ray. Calculations of this Madler, have added greatly to the number of objects either as delineated on their maps or referred to in and the consequence is that the entire question remains involved in doubt. During the last seventheir letterpress. Lohrmann appears to have carefully studied Schröter's results, as we find him teen months as many as 1,227 observations of the quoting the measures obtained by Schröter in spots on Plato alone have been made; and althonge S the 1st of October will usher in a new order several instances. On examining the results of the the varying state of the earth's atmosphere affects of things in the postal service of the country, two greatest selenographical works of the present in no slight degree the visibility of such delicate we desire to call the attention of our readers to the century, and comparing the one with the other, we objects, phenomena are presenting themselves which advantages it offers to the community at large, and find precisely the same kind of phenomena present. call for a much more rigorous treatment than bas in particular to the correspondents of the ENGLISH ing themselves which in a great measure perplexed yet been accorded to them. The affirmation of MECHANIC. We already foresee that the numerous Schruter; but as Lohrmann and Madler worked inde- change on, or quiescence of, the moon's surface must communications, in the shape of Replies and Queries, pendently of each other, and Madler evidently had depend, not upon the accumulation of desultory that we hourly receive, will be largely augmented. very low idea of the value of the preceding labours of and undiscussed observations, but upon such as are On the 1st of October our readers will be able to Schröter, these phenomena passed unnoticed at the undertaken on a well-arranged system, and disobtain a packet of twenty-four cards for 18., or a time. Upon comparing the three for the purpose of affecting them. The present state of the ques cussed with reference to every known agency capable single card may be purchased for the sum of one of elucidating the history of any given object, such halfpenny. They will be of the size of an ordinary results as these are frequently obtained. An object tion is, therefore, one of doubt-one that calls for letter; blank on one side to receive the communica- is found in Schröter, designated by a Greek or other observation of the most vigorous character and tion; while the side on which the address is to be character, and its appearance described in his discussion of the most rigorous nature to settle it. written will bear the stamp. These cards must be text. posted without envelopes, and without any extrasurface, but discussion in various ways is behind Observation of late has been tending towards registration of minute detail detected on the moon's neous attachment whatever. Sufficient room will thus be afforded for some of our correspondents to the requirements of selenography, and until it can write their Queries and Replies. In addition to the keep pace with observation the doubt alluded to halfpenny card, there is the reduction of the postage above must remain. on newspapers. Our readers will be able to send a copy of the ENGLISH MECHANIC to any friend in the United Kingdom for a similar charge of one half-graphy would be greatly advanced. His chart must ON THE PRESENT POSITION OF CHEMICAL penny; but two or more sent in the same wrapper will require a stamp for each; although, by the Printed Matter" Post, newspapers up to two ounces in weight may be sent for a halfpenny.

PARAFFINE INDUSTRY.

Lohrmann, but given on Beer and Mädler's map;
This object may be altogether omitted by
and objects are by no means rare which may be
found in Lohrmann, but omitted by Beer and
Madler, and vice versa.

Were the results of the labours of Julius Schmidt
during a period of nearly 30 years given to the public,
there can be no doubt that our knowledge of seleno-

contain a large proportion of the objects previously
recorded by Schroter, Lohrmann, and Beer and
Madler, and judging from the instances already

SCIENCE.

PROFESSion of the British Association, thas
ROSCOE, in his opening address

described the progress and present position of
Chemical Science :-With regard to the position of
chemical science at the present moment, it will not
take a careful observer long to see, that in spite of
the numerous important and brilliant discoveries
of which every year has to boast, we are really but
very imperfectly acquainted with the fundamental
laws which regulate chemical actions, and that our
knowledge of the ultimate constitution of matter
upon which those laws are based is but of the most
elementary nature. In proof of this, I need only
refer to the different opinions expressed by our
leading chemists in a discussion which lately took
place at the Chemical Society on the subject of the
Atomic Theory. The President (Dr. Williamson)
delivered a very interesting lecture in which the
existence of atoms was treated as "the very hic
of chemistry.' Dr. Frankland, on the other hand.
states that he cannot understand action at a dis-
tance between matter separated by a vacuous space,
and, although generally granting that the atomic
theory explains chemical facts, yet he is not to be
considered as a blind believer in the theory, or as
unwilling to renounce it if anything better pre-
sented itself. Sir B. C. Brodie and Dr. Odling both
agree, that the science of chemistry neither requires
nor proves the atomic theory; whilst the former
points out that the true basis of this science is to
be sought in the investigation of the laws of gaseous
combination, or the study of the capacity of bodies
for heat, rather than in committing ourselves to
assertions incapable of proof by chemical means.

alluded to, of apparent omissions by one or other of the above-named observers, it is highly probable that the number of such instances would be much increased. The value of his measures (4000) of the altitudes of lunar mountains for comparison with N the Paris Exhibition of 1855 was shown a I block of a fine, with a few candles. or addition to those of Schröter and Madler, canFew not admit of a doubt. His published catalogue of visitors understood what it was, and no one could rills is very valuable in this respect. It is to have anticipated the great extent to which the Schmidt that we are indebted for one of the most trade in this article would subsequently be pushed. important announcements bearing on the subject of The manufacture of paraffine candles has become Lunar Activity, that of a change in the crater an important industry, and there are single esta- Linne, which," says Madler (Report, British blishments in Germany capable of turning out Association, 1868, p. 517), "has hitherto offered the 240,000 candles daily. In England and France the only authentic examples of an admitted change." industry has reached vast proportions, and in He had previously said (same report), "What has America it has no mean significance. Wagner esti- lately been observed in the crater Linne proves at mates the production of paraffine in Prussia alone all events that there real changes have taken place for the year 1870 at 11,000,000lb. The brown coal and that too under circumstances even visible to us." of Germany, and the boghead of Scotland, and the Further on, however, the great selenographer reRangoon petroleum are particularly well adapted to marks that on the 10th of May, 1867, his eye having the production of paraffine, while Bohemian and undergone an operation for cataract, he attempted Austrian, and other continental coals, yield a very an observation of Linne in the heliometer of the small quantity. The uses of paraffine are many. As observatory at Bonn, and found it shaped exactly its melting point is low, it is proposed to employ it and with the same throw of shadow as he rememfor the preservation of meat. Meat several times bered to have seen it in 1831. "The event," he immersed in a bath of melted paraffine will keep says, "of whatever nature it might have been, must for a long time, and when wanted it is only neces- have passed away without leaving any trace obsary to melt off the adhering wax-like coating to servable by me." The doubt still hanging over this prepare it for cooking. For stoppers to acid bottles, object is well known, and it may be regarded as to coat paper for photographic and other uses, as a furnishing at least one of the instances of the lubricator, for candles, as burning oil, to coat pills, present state of the question of activity. The unin the refinery of alcohol and spirits, paraffine now certainty attaching to the question of change in this finds ready use. It has also been employed for the particular instance mainly arises from the difficulty adulteration of chocolate and candies; for the pre- of deciding upon the accuracy or otherwise of the Agreeing in the main myself with the opinions of servation of railroad timber; to saturate filter delineations of Lohrmann and Beer and Madler, the last chemists, and believing that we must well paper for certain purposes; to coat the sides of although both describe it as showing a diameter of distinguish between fact and theory, I would remind vessels in which hydrofluoric acid was to be kept; 5 or 6 English miles. Generally speaking the ob- you that Dalton's discovery of the laws of multiple to preserve fruit from decay; for oil baths of conservations between October 1866 and July 1867 all and reciprocal proportions, as well as the differences stant temperature; to prevent the oxidation of the agree in its present appearance differing greatly in the power of hydrogen replacement in hydroprotoxides; to render fabrics waterproof; as a from that which it must have presented according chloric acid, water, ammonia, and marsh gas, are substitute for wax in the manufacture of matches; to the delineations and descriptions of the two fucts, whilst the explanation upon the assumption