when the sea bottom of the Gulf of Mexico shall have been more accurately surveyed.

THE last Report of the Juvenile Literary Society of the Friends' School, Croydon, shows that natural history is in no way neglected by the members. Twelve boys have been collecting British plants, two collections are being made to illustrate botanical terms, and two to exemplify the British ratural orders. Nearly three hundred "varieties" (? species) of plants in flower have been exhibited in the school-room, and some additions to the flora of the district have been discovered. Observations on the weather and the recurrence of natural phenomena have been kept up; and collections illustrating the ornithology and conchology of the district are in progress. Additions to the library and museum are acknowledged, and the treasurer's report shows a balance in hand.

THE Transactions of the Maidstone and Mid-Kent Natural History and Philosophical Society for 1870 are chiefly remarkable for their total want of local matter. Papers are printed on "Sericiculture," "The Nervous System,” “Skin and its Appendages," "Natural Selection," "The Similarity of Various Forms of Crystallisation to Minute Organic Structure," and "The Geometrical Structure of the Hive-Bee's Cell," none of them containing anything new, although of average ability; but we look in vain for any information as to the fauna or flora of the district. Classes in connection with South Kensington in Mathematics, Electricity and Magnetism, and Inorganic Chemistry, have been established, and the number of members is on the increase.

WE learn from the Melbourne Argus that the past efforts of the Acclimatisation Society, and of private individuals working with similar objects, have been only too successful. Rabbits and sparrows are now so abundant that in many districts they are a complete nuisance, and vigorous efforts are being made to extirpate them, or at any rate to reduce their nunibers. Hares are so numerous in the neighbourhoods of Melbourne and Geelong that it is proposed to modify the restrictions hitherto imposed upon their destruction, and to allow clubs, upon payment of a moderate licence fee, to course them.

THE account which has been published of the terrible ravages caused by the plague in Buenos Ayres, reads like so many pages from the description of the Great Plague in London. During the months of March and April last the city was almost entire'y deserted, everyone who could fleeing into the country. The deaths increased from the daily average of 120 in January to 640 on the 4th of April and 720 on the 5th, whilst on the 6th of April 500 entries at the cemetery were registered up to noon. From this time, owing to the exodus of people, the ravages of the plague began to diminish, and there is every reason now to hope that it may soon be stamped out. In one cemetery alone 20,000 corpses were buried, and for this purpose large trenches were dug, in which the bodies, some coffined, but many merely swathed in their bed clothes, were shot out of carts and quickly covered with lime. Attempts of all sorts were made to stay the plague, but unavailingly, and whilst the native doctors fled the spot, to the credit of the few English medical men there, it is universally allowed that they worked most nobly and disinterestedly through all the terrible time. We read of "coffins being hawked about the streets, while empty carts touted for their silent passengers; of people stricken with fever deserted by their friends and relations and even their children, and left to die without medical attendance or even food and water; of the shrieks and cries of delirious patients that made night hideous; and of the corpses that were constantly found by passers-by in the early morning of people who had been seized with the death agony in the streets during the night time." The cause of all this horror and misery is described as purely local, and due to the total absence of drainage and the terrible overcrowding of

the houses and localities where the poor reside, and the long continued neglect of the most ordinary sanitary precautions. Surely this is a terrible lesson to those who wilfully and criminally neglect the reiterated teachings of science.

A SINGULAR instance of canine madness in a horse is recorded in a recent number of the "Zeitschrift für Parasitenkunde." Ahorse which had been some time before bitten by a dog supposed to be mad, was brought to the hospital of the Royal Veterinary College at Berlin, suffering from an uncontrollable propensity to bite, not only men and other animals but any hard substance, and even its own body, by which it had severely injured its mouth and broken several of its teeth. After its admission to the hospital, this propensity was violently manifested in fits, preceded by remarkable convulsive movements, after which it would fall suddenly, and remain for a time perfectly motionless, becoming gradually weaker after each attack. It had refused food for two days, and died without a struggle on the evening of the day on which it was admitted. An examination showed no organic disease, but considerable internal inflammation.

WE have received from Prof. Hinrichs, of the Iowa State University, U.S., the first two numbers of the School Laboratory of Physical Science edited by him. The object is to supply a defect stated in the prospectus to be as flagrant in America as it is in England, that their schools, while very excellent in regard to the literary branches, neglect nearly all departments of science. The numbers which have already reached us contain original articles on Physical Science, laboratory notes and news, chronicles of observations, and reviews of books. They are illustrated by lithographs, and published at a low figure. We commend the publication to all those interested in the progress of Physical Science in America, and anxious to further the same. add that the publication is maintained at a considerable loss to the editor, and it is doubtful whether it can be carried on unless it receives the extraneous support which it so well deserves.

We may

A TERRIBLE and most disastrous tornado is reported from Dayton, Ohio, U.S., on the 9th of July, by which eight people were suddenly killed and more than fifty seriously injured. The damage done to property was immense, hundreds of houses and churches were unroofed, bridges were carried away, trees were lifted up by their roots, and locomotion of all kinds was stopped, and in the country very large quantities of wheat and grain were completely ruined.

SINCE we noticed the appearance of the first part of Messrs. Sharpe and Dresser's "History of the Birds of Europe' (NATURE, April 27), three more parts have appeared, each containing eight or nine beautiful plates, and the usual copious letterpress. Among the former we may notice those of the pigmy owl (Glaucidium passerinum), the white-tailed lapwing (Chettusia leucura), the great black woodpecker (Dryocopus martius), and the red-backed shrike (Lanius collurio), as being especially admirable pictures of bird life; while the fact that twelve pages of letterpress are devoted to the bearded reedling (Calamophilus biarmicus), fourteen to the great black woodrecker, and the same to the hobby and eider duck, will give some notion of the labour and research devoted to bringing together all the reliable evidence on the habits, distribution, structure, and affinities of the several species. Instead of making the pictures everything, as has sometimes been done in illustrated works on natural history, we have here really a "history" of all the more important known facts relating to each European bird. We sincerely hope that a work which the authors evidently spare no pains to make as good as possible, may meet with the liberal support it deserves.

We understand that the eruption of Mount Vesuvius, which has been more or less continuous during the past six months, and which has lately increased considerably in violence, is

causing great apprehension as to the safety of the Italian observatory of Vesuvius. The lava has already partially submerged the hill of the Canteroni on which the observatory stands, and the immediate erection of a strong dyke of scoria so as to divert the stream of lava is urgently asked for.

WE are requested to state that the terrible earthquake at Bathang in China, of which we lately published an account (NATURE, vol. iv. p. 45), occurred on April 11, 1870, and not this year, as might be inferred from the description.

THE American Polar Expedition in the steamer Polaris (Capt. Hall) left Brooklyn on June 29th. Dr. E. Bessels, of Heidelberg, who was Scientific Director of the German Expedition to Nova Zembla in 1869, is appointed to the same position on this expedition. The vessel is provisioned and equipped for two-and-a-half years' absence, but the explorations may be continued longer it Capt. Hall desires it, and fresh supplies will be sent. The expedition is undertaken principally for geographical discovery, but every opportunity will be made use of to make scientific observations and experiments, for which purpose a long series of instructions have been drawn up by a committee of members of the Academy. These consist of Prof. Henry on meteorology; Prof. Newcomb on astronomy; Prof. Higlard on magnetism; Prof. Baird on natural history; Prof. Meek on geology; Prof. Agassiz on glaciers. Orders have been given that small copper cylinders containing letters, scientific intelligence, &c, shall be frequently thrown overboard during the progress of the expedition, and these, when found, are to be sent to the Navy Office and afterwards published.

A MOST important discovery is announced from the Isthmus of Panama. In the district between Aspinwall and Panama, and extending over a large area, valuable beds of coal have been discovered and recently fully explored. The quality of the coal has been tested and most favourably reported on. These mines can be worked to great advantage, and the seams are rich and extensive, and there is ample water communication to the coast by means of the river Indis. If further investigations confirm this preliminary report, great benefit cannot fail to result to commerce in the Atlantic and Pacific Oceans from this opporture discovery.

THE GUN-COTTON EXPLOSION AT
STOW MARKET

THE
HE disastrous explosion of gun-cotton, which occurred
on Friday last on the premises of the Patent Safety
Gun-cotton Company, is a calamity of unusual significance.
Besides the large number of killed, amounting, we believe,
to five and-twenty persons in all, there were as many as
seventy ma med and injured, many of them too, in such a
manner as only violent explosions are known to torture and
lacerate their victims; and when it is taken into consi-
deration that in all probability a dozen tons of the material
actually exploded, the grave nature of the accident is in
truth not surprising. The whole group of factory-build-
ings and out-houses were levelled to the earth at one fell
swoop, and for miles away the effect of the catastrophe
was acutely felt.

But it is not only from a social point of view that the affair is to be deplored. As a result seriously affecting the science of explosives, the occurrence is peculiarly unfortunate; for the belief in the safety of gun-cotton as an industrial and military agent will now be gravely shaken. It is all very well for scientific men to adduce a plausible reason for the occurrence, and to prove conclusively that with due care and precaution a disaster of this nature could not possibly have happened; but the public unfortunately will not be satisfied with a theoretical assurance of this kind; and indeed measures should certainly be taken, not only to guard against such wholesale death and destruction, but to render the same absolutely impossible.

The true cause of the disaster we can scarcely hope to discover; but, leaving out of consideration any personal carelessness on the part of the workmen, the ignition of the cotton must either have occurred through the acci dental firing of a cartridge, or primer, or through spontaneous combustion. It is well known that pyroxilin may be exploded in two totally distinct ways-that is to say, either by inflammation or detonation. In the first instance the cotton, unless confined, only burns fiercely, and does not explode like gunpowder on the instant; while, on the other hand, if it is ignited by detonation or percussion, the material acts in the same violent manner strophe at Stowmarket, then, the result of detonation, or of as nitro-glycerine or fulminate powder. Is the catathe milder form of explosion, such as inflamed gun-cotton confined in lightly-built magazines would produce? If sporting cartridges, such as contain a small charge of fulminate or detonating primers, were at all near the spot, the culpability of the authorities is very great indeed; for the approximation of the two agents constitutes obviously that so thoughtless a proceeding could have been possible. a source of extreme danger, and it is really hard to believe At the same time, if a detonation actually did take place, as in fact some of the results would lead us to believe, then there is no other way of explaining the occurrence.

In regard to the theory of spontaneous combustion, we must not be too eager to draw conclusions, as the careful experiments recently made by Prof. Abel distinctly prove that decomposition in this wise is almost impossible, provided the pyroxilin has been carefully manufactured. Truly, if such has not been the case, and there existed impurities or imperfectly converted masses in the store of gun-cotton at Stowmarket, then a valid reason for the explosion is no doubt at hand. Still it must be remembered that pyroxilin only takes fire at a high temperature (300° or 350° F.), and therefore we must suppose that not only was the recent hot sun allowed to shine uninterruptedly upon the magazines, but that the latter were, moreover, very badly ventilated, and altogether ill cared for. Again, to have produced such wide-spread devastation, the stores or outbuildings containing the cotton must have been somewhat strongly and firmly built, otherwise there would have been no resistance to the burning mass, and consequently no violent explosion, for it must be borne in mind that the more completely the charge is confined, the inore energetic will be the result.

Under any circumstances, then, we must come to the conclusion that either the gun-cotton was strongly confined in cases or magazines and simply inflamed, or that the material was detonated by a charge of fulminate powder; and in whichever way the accident happened, the same was in great measure due to neglect and carelessness. Why, indeed, such a large store of dry guncotton should have been kept so near a populous factory it is hard to understand; and inasmuch as the compound is always prepared in a wet, and, consequently, harmless condition, it would appear that the desiccation of the mass is afterwards carried on in close proximity to the less dangerous departments of the works. It is truly lamentable that, after the prolonged researches of Schönbein, Abel, Brown, and others, the information and particulars brought to light should not have been more appreciated and made use of by those so directly interested in the matter; for one cannot help thinking that if the business of the Stowmarket Company had been carried on under competent scientific supervision, we should not now have to lament so deplorable an accident.

While then we must all deeply regret this sad occurrence it is to be hoped that the favourable judgment passed upon gun-cotton by scientific men during the last ten years will not be completely ignored; but that, on the contrary, a proper use may be made of the valuable information at our disposal by employing it in the framing of regulations to govern more strictly and efficiently_the manufacture of explosives. : H. B. P.

It was a happy chance that directed my fingers, in an idle mood, one day in March of last year, to the top of a stiff twig that sprang from the stool of an old acacia, and rose to a height of about three feet, where it had been lopped by the gardener's knife. Pulling the twig aside, and letting it fly back by its own elasticity, I noticed the path which its top traced in the air; it was not difficult to follow its course, for the raw section of the wood was white and caught the eye, and the motion was not very rapid, the twig being rather slender for its height. I had often noticed-everyone must have noticed-odd behaviour in

FIG. 6.-Proportion 1 : 2.-Looped type.*

springs of various kinds before this, but the motion had been too quick or too slow to show the law that governed it. On the present occasion I could see that the twig began at once to deviate from the plane of its first vibration, and to describe an elliptic path, the ellipse growing wider and shorter till it was nearly circular, then still wider and still shorter, till its width exceeded its length, and it was again elliptic, but the long axis now occupied nearly the position of what was the short axis before. The new ellipse still grew narrower at every vibration, and

* Figs. 7-12 will be found in the second part of this article.

at last became a straight line in a second plane at right angles (roughly speaking) to the first. The vibration continuing, the twig began to retrace its path, and returned to the plane in which it started, by a complete recantation of its former errors, though the gradually failing strength of its oscillation was gradually diminishing the range of its orbit. No sooner was the original primary plane regained, than it was again forsaken for the secondary, the errant twig repeating its delirious maze of elliptic gyration, but always with a method in its madness, across and across, again and again, till it finally came to rest in the centre of its web, still striving to the very last perceptible tremor to persevere in its life-long career of consistent vacillation.

Repeating the experiment again and again, I found that there were two planes, at right angles, in either of which the twig would vibrate obediently, without deviation to one side or the other, and that the primary and secondary planes of the first experiment made equal angles with either plane of obedient vibration. When the twig was started only a few degrees on one side of either plane of obedience, its elliptic error carried it into a secondary plane only a few degrees on the other side, and then back again and again; while if the primary plane was chosen half-way between those planes of obedience, in opposite quadrants, then the secondary plane was found to lie half way in the alternate quadrants, at right angles to the primary.

How to explain this phenomenon was a puzzle, till my father hinted that its law might lie in a difference of periods of oscillation in those two planes of obedience, caused probably by the curved shape of the twig or perhaps by its elliptic section, at any rate caused by some condition which made the twig vibrate as a short spring with short period in one direction, and as a long spring with long period in another direction at right angles to the first.

This hint gave the key to the puzzle, and it was easy to demonstrate that all the phenomena would necessarily follow on such an assumption. Laying down two systems of rectangular co-ordinates to represent the spaces described in so many units of time (the motion of the twig being resolved in those two directions at right angles), and making such spaces in one direction and n+1 in the other, we had a diagram on which we could trace the twig's path, beginning at one corner and drawing the diagonals in the successive rectangular spaces. If there were such spares in both directions (which would represent equal periods of oscillation), our course of diagonals would only carry us into the opposite corner, with no alternative but to retrace the same line to and fro without deviation; but since in one direction there remains one space over when we reach the border of our diagram, our course of diagonals carries us across the corner, and our path returns with the width of one space between it and i's former self; in like manner, on reaching the border of the diagram near the starting-corner, the course of the diagonals carries us across to the other side of our first track, and we make a second journey only to wander still farther from our first path in the return. The error increases at every turn, till at last the path of our imaginary twig finds itself wholly forgetful of the corners with which its shuttle-play began, and giving all its allegiance to the alternate pair. At last our diagonals are all described, and we find that they end in one corner or the other according as n is even or odd, and the twig must then be supposed to retrace its maze. If we make our spaces all equal, the track of our twig looks very angular, like the path of a cracker; but if we endeavour to imitate the truth by greatly diminishing the marginal spaces, our diagonal track becomes bent into a series of quasi-elliptic curves, which represent with tolerable accuracy the path of our twig, if we suppose it to vibrate without frictional retardation (see Fig. 13).

We shall get the due diminution of the marginal spaces by drawing our two sets of parallel lines through two sets of points in the circumference of a circle, equidistant for each set, but allowing only n equal spaces in the semicircumference for the n period, and n+1 for the other. Introducing friction, we have a gradual diminution of the orbit, which brings our twig finally to rest in the centre of the diagram. But this friction has greater effect in the direction of shorter period, because our twig has to make n + 1 journeys in that direction to n in the other, consequently the range of the orbit in the former direction will undergo more rapid contraction than in the latter, and the twig will sooner come to rest in the one plane than in the other; so that if there is large disproportion between and +1, there will remain a residue of surplus vibration in the direction corresponding to the long period after all motion in the cross-plane has been arrested. This is easily seen by experiment on a twig that vibrates much more rapidly in one direction than in the other.

Having a desire to get a permanent record of the fleeting footsteps of my acacia twig, I forced the butt-end of a small dance-pencil into the soft pith in the centre of the top-section, and set the twig vibrating with one hand, while with the other I held a sheet of note-paper in contact with the pencil-point. As might be supposed, the result was not satisfactory, but very suggestive. The twig was not strong enough to overcome the resistance of friction between pencil and paper, and the hand-suspension for the latter was very inefficient. I soon found an upright hazel stem nearly an inch in diameter, possessing all the vibratile properties of my slender acacia-twig with much

FIG. 13.-Diagram showing approximately the theoretical path of a spring vibrating without friction, with periods of vibration in cross-planes in the proportion of " to +1. (= 10.) A and B are the beginning and end of the cycle, perpetually retraced, and are analogous to the two cusps of Fig. 9 or Fig. 11.

greater strength, and transferred my pencil to its new abode. For suspension of paper I erected a wigwam of four poles round the hazel, and stretched a quarto leaf by india-rubber bands from the four poles to the four corners close above the pencil. Then pulling the hazel aside, I adjusted the paper-suspension till I was sure of good contact with the pencil, and then let go :-buzz-a momentary rustle under the paper, and the thing was done; and, on loosing the elastic bands, I found the path of my pencil-point faithfully traced in delicate lines, which the eye could follow from the starting-point till lost in the mazy confusion of the centre where the manifold crossings and recrossings were inextricably entangled. By starting the hazel again and again, leaving the paper undisturbed,