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waters of the Tamina.” The only points in Prof. Tyndall's is devoted to a résumé of the “viscous” and “regelation description to which we a little demur are when he speaks theories of glacier motion ; a controversy which can hardly of the traveller“ passing along the chasm midway between yet be regarded as concluded, seeing that the experiments top and bottom," the fact being that the well-known of Mr. Mathews and Mr. Froude, to which Prof. Tyndall gallery is only a few yards above the Tamina ; and where briefly alludes, appear likely to have a very important he quotes the gorge as an illustration of water-action upon bearing upon the question of whether or not ice under limestone rock. It is true that the strata here are not any circumstances is a flexible or plastic substance to an crystalline, and they may be occasionally calcareous, but appreciable extent. we should hardly venture to apply the name of limestone Among the very miscellaneous scraps with which to the hard black shales or slates out of which the gorge the volume terminates, is an account of the voyage to itself is cut. Professor Tyndall also omits to call atten- Algeria to observe the Eclipse. This, so far as its tion to the close connection between the direction of the main purpose went, was a dismal failure, but remarks principal joints and the form of the gorge. This are introduced on the colour of the sea and sky, a subject is especially noteworthy at Pfäffers, where the chasm already treated by the author in his “Glaciers of the is not vertical, but inclined to the horizon at an angle of Alps.” During the voyage home a number of bottles of some 70°, the water having followed, as is its wont, the sea-water were secured from various stations, which were direction of least resistance, viz., one of the sets of joint afterwards examined in London by passing through them planes. The gorges of the Pantenbrücke, the Aar above a beam of electric light-the purity or impurity of the Im-Hof, with many others, might be quoted as instances water is then shown by the less or greater amount of light of the same. We think, indeed, that in arguing against which it scatters. Briefly, the result was that the dark those who ascribe alpine sculpture mainly to fracture, blue water was very pure, the cobalt-blue rather less so, the professor does not quite do justice to the influence which while the green tints denoted the presence of much susfissures, faults, and joints (which last may, in many cases, pended matter, and the yellowish green was very thick. be connected with the others) ise in directing the A remarkable instance of this variety of colour which, if meteoric agents. These have not, indeed, fashioned the our memory serve us, he has not quoted, is in the Lakes mountains, but they have obliged the sculpturing forces of Thun and Brienz; the waters of the latter, which reto work in certain directions, have been like the rails or ceives the silty streams of the Aar and the Lutschine, are the points which cause a locomotive to follow a particular distinctly green, while those of the former, into which no course instead of wasting its power in wandering over the important glacier torrent directly enters, are of a beautiful fields.
blue. Further on in the chapter, Prof. Tyndall refers to his
In fine, though there is little new about the book, own favourite theory of glacier sculpture, with regard to
many of Prof. Tyndall's admirers will be glad to possess which he expresses himself more guardedly than in the in a convenient form so many thoroughly characteristic paper originally published in the Philosophical Maga- papers, displaying at once his thoughtful mind and zine (vol. xxiv. p. 169). Still we cannot say that we are
intense love of nature, as well as his great command over convinced by his arguments even in their modified form. nervous and picturesque English.
T. G. BONNEY No one, of course, would deny that a glacier can deepen its bed ; the question is simply one of degree. With regard to this our space will allow us to do little more than
OUR BOOK SHELF express dissent, and indicate one or two points where, The Natural History of Plants. By H. Baillon. Transwhile not disputing Prof. Tyndall's facts, we cannot ac
lated by Marcus M. Hartog. Vol. I. (London : L. cept his inferences.
Reeve and Co. 1871.) The silt which is brought down by a glacier stream
HAVING noticed, on its publication, the first volume of cannot, we think, be taken as a measure of the abrasion
Prof. Baillon's "Histoire des Plantes” (see NATURE, exercised by the glacier ; surely the greater part is de- vol. i., p. 52) we need scarcely do more than call attenrived from the stones crushed between the ice and rock ; tion to the English edition which now lies before us. The it is the grist from the glacier mill, rather than the detritus translation, we may say at the outset, appears to us to be of the nether stone. We fail also to see how, unless well done ; the meaning of the original is, as far as we under exceptional circumstances, a glacier can“ do more ledge of his subject is shown by the translator than is
have observed, carefully preserved ; and a better knowthan abrade." Granted that “rocks are not homo- always the case in English renderings of foreign scientific geneous, they are intersected by joints and places of works. The co-ordination of the natural orders followed weakness which divide them into virtually detached in the work is, as was mentioned in our notice of the masses,” we doubt if it follows that “a glacier is un- original, novel ; whether it will stand is a question on doubtedly competent to root such masses bodily away.”
which we ought not, perhaps, to express an opinion until A heavy body sliding over such masses and in close con
the plan is more fully developed. We could have wished
that the author had given in this first volume some general tact with them, would, we think, be more likely to keep sketch of his new system, with a defence of its peculiarithem in their place, and certainly rocks from which ties. So competent an authority as Prof. Baillon cannot glaciers have retreated do not exhibit evidence of this have departed from the ordinary arrangement without kind of erosive action. We confess, therefore, to still cogent reasons, which we should have liked to have known. regarding the effects of glaciers as comparatively super- know the views of their fellow-workers on the Continent.
It is always a great advantage to English systematists to ficial, and classing the ice ploughs of past ages as among We miss also the great assistance that is afforded to the the efforts of scientific imagination.
systematist by a tabulated clavis of the genera belonging A considerable portion of the latter part of the volume to each natural order. The amount of information con
tained in the volume as to the various relationships of he speaks of the theory of Natural Selection, he cannot claim to the natural orders described in it, the morphology of their have added much to the world's philosophical opinions. genera, the distribution of the different types, and the
He then complains that I have only toucherl one of the many
facts relied upon by Darwinians ; I refer him to my letter, in economic products obtained from the species, is immense. It possesses, however, the defect so common in foreign and that I have many more which will follow if the Editor have
which I distinctly say that it contained only one of my ohjections, scientific works, of the absence of any table of contents patience with the discussion. The reply to Mr. Wallace will or index to the subjects treated of. Had the publishers of confine me, however, in this letter to the ground covered by the the English edition supplemented the index of genera former one. Having disposed of the formal and personal matand subgenera with one referring to the various topics ters, I now approach the matters of fact about which we are at discussed, they would have rendered the English edition a
issue. practically more useful contribution to botanical literature Here, I am sorry to say, I am met in a very different spirit by
Mr. Wallace to that in which Mr. Darwin meets objections. Dogmatism, bold and unwavering, was the privilege of the philosophy of the Schools, but in the 19th century it is puerile. Mr. Wallace states boldly, without any authorities, merely as an imperial ipse dixit, that the most vigorous plants and animals are the most fertile. I had, at least, ihe decency to quote the book of Mr. Doubleday, containing a magazine of facts and examples in support of my view, and which tells exactly the other way.
This view has not been correctly stated by Mr. Wallace. The position I maintain is this, that, as a general law, those individuals which are underfed and lead precarious lives, are more fertile than those whose advantages make them vigorous and healthy. The ringing of the bark and the pruning of the roots of barren fruit trees and the starving of domestic animals to make them fruitsul were examples to this end.
Mr. Wallace quotes only one example in his own support, and I will accept it as a crucial test of my position, which he will acknowledge to be fair ; the case of the Red Indian and the Backwoodsman. The Red Indian lives entirely on flesh, the Backwoodsman almost entirely on vegetable food. Like meat livers in every part of the world, in Mexico, on the River Plate, in Siberia, in Turkestan, and in some parts of Russia, the Red Indian is not a fertile creatire. The Backwoodsman, like vege. table feeders everywhere who are not luxurious, in India, China, Poland, and the Russian provinces bordering on it, Ireland, &c., is comparatively fertile, but only comparatively. It is a mistake to suppose that the Backwoodsman is specially fertile, and in a few years he becomes, as the inhabitants of Kentucky and Tennes-ee have been long known to be, diminishing in numbers,
the population of the States being kept up by immigration. CALYCANTHUS FLORIDUS: Floriferous shoot.
Mr. Chadwick, in his “Sanitary State of the Labouring Classes,”
observes that where mortality is the greatest there is much the than the French original. The illustrations are profuse, greatest fecundity; thus, in Manchester, where the deaths are and of that excellence which we look for in vain in works one to twenty-eight, the births are one to twenty-six, while in originally published in this country. We append one of
Rutlandshire, where deaths are but one to fifty-two, births are one the well-known “Allspice Tree,” the Calycanthus floridus.
to thirty-three, showing that a state of debility of the population
induces fertility, This only supports the common dicta of The small order Calycanthaceæ, including only the
doctors that consumptive patients are generally very fertile. American Calycanthus and the Japanese Chimonanthus,
The pastoral tribes of Eastern Russia which have recently taken is one the true position of which has been much disputed to agriculture, such as the Tchuvashes, &c., have begun to inby systematists. Baillon makes it a series” of Moni. crease most rapidly. The Hottentots at the Cape, who were miaceæ, with which he also unites the Australian Athero- formerly a numerous race living very hard lives, are almost extinct spermeæ, bringing this order forward from its usual posi- now that they are carefully tended and well fed. The Yeniseians, tion among the Incompletæ to close alliance with Magno- the Yukahiri, and other Siberian tribes, have disappeared like liaceæ and Anonaceæ.
A. W. B.
smoke before the advance of Russian culture ; they have suffered little if at all from the Russian arms.
Let me quote a curious example in answer to Mr. Wallace
from the very race to which he has referred. Captain MusLETTERS TO THE EDITOR
ters, in describing his recent journey through Patagonia at
the Anthropological Institute, told us that it was the custom for [The Editor does not hold himself responsible for opinions expressed the Patagonian women to be bled at certain times referred to,
by his Correspondents. No notice is taken of anonymous as they believed it made them fertile. Among the Patagonians, communications. ]
therefore, we meet with empirical witnesses, unsophisticated
by our philosophy, to the truth of the position I maintain. A New View of Darwinism
But those who live in large cities need not travel to Patagonia. I HAVE only just seen the two letters in answer to one from The classes among us who teem with children are not the
on Darwinism which you were good enough to insert in well-to-do and the comfortable, but the poor and half-sed NATURE, and to which I ask the favour of being allowed to Irish that crowd the lowest parts of our towns. I am not reply. I have to thank Mr. Darwin for his references and for contrasting now the fat with the lean, but the comfortable classes the tone of his letter, which is in such marked contrast to the with those who lead precarious lives--the vigorous in health with angry dogmatism of Mr. Wallace.
the sickly, the half-sed, and the weak. It will be asked, why Mr. Wallace commences by ridiculing the phrase the Per- rely so much upon man? The answer is that I quite agree with sistence of the Stronger. The phrase was not mine, it has been Mr. Darwin that man is subject to the same natural laws as the used by a better man than I, namely, by Prof. Jowett, and it animals, and further I believe that since we have studied man has the advantage of not involving an identical expression, which more closely and under a greater variety of conditions, facts de. the Survival of the Fittest does. "That those forms of life survive rived from our experience of man are of greater valre than those which are best adapted or best fitted to survive," is not a very deduced from our examination of the other animals. profound discovery; it might have suggested itself even to a But let us turn to these latter for a space; and here I tread child, and if Mr. Wallace means nothing more than this when ! with much greater diffidence, for I am aware of the vast ex
July 13, 1871)
perience and fund of illustration possessed by Mr. Darwin, and I cowslips to the greenhouse, their flowers grow double, and they
H. HOWORTH breed. Mr. Bates, in his admirable work on the Amazons, strongly insists on similar cases, and he remarks that the fact of thoroughly tamed wild animals and birds not breeding when MR. Wallace has effectually set aside Mr. Howorth's new kept by the Indians, cannot be wholly accounted for by their views on Darwinism, and it now only remains to point out that negligence or indifference, for the turkey is valued by them, and the latter gentleman, in his instances, puts the cart before the the fowl has been adopted by the remotest tribes. In almost horse. Hens that are fat and don't lay are fat because they don't every part of the world, for instance, in the interior of Africa, lay. When the sexual powers, either in plants or animals, are and in several of the Polynesian islands, the natives are ex- defective from accident or design, the overgrowth always takes tremely fond of taming the indigenous quadrupeds and birds, place, and this among animals is chiefly by the increase of but they rarely or never succeed in getting them to breed,” and adipose tissue. so on, through sixty pages of closely-packed examples. And what Birmingham
LAWSON Tait is Mr. Darwin's commentary on these facts ? I again quote page 158:-“We feel at first naiurally inclined to attribute the result to loss of health, or at least to loss of vigour, but this view can
Recent Neologisms hardly be admitted when we reflect how healthy, long-lived, and vigorous many animals are under captivity, such as parrots and
I have been long accustomed to register the first appearance of hawks when used for hawking, chetahs when used for hunring, and
new words and phrases. Of course the vast majority of these take elephants. The reproductive organs themselves are not diseased,
no root, perishing where they fall. Here is a sample of the latest and the diseases from which animals in menageries usually perish and impolury, which were brought in by tiie Franco-Prussian War,
issue : Survial, introduced, I think, by Darwin ; indisciplire are not those which in any way affect their sertility. No domestic animal is more subject to disease than the sheep, yet it is remark
and also the vulgarism to telegram. The greatest atrocities in this ably fertile.” Mr. Darwin, with equal clearness and conclusive line are committed by physicists,” if the shade of Faraday wil ness, decides that this sterility cannot be due to a failure of pardon me the use of that word; and far away the worst coinage sexual instincts, change of climate or of food, or want of food or
I cver encountered is due to Mr. Alfred R. Wallace. As it is exercise ; and he concludes that certain changes of habits and of
“meet and right and our bounden duty" to stigmatise such inlife affect in an inexplicable manner the powers of reproduction. truders, and if possible prevent their adoption, I take the liberty But what is true of 'man it is reasonable to suppose is true of all of making my feeble protest against Mc. Wallace's " prolificness, these instances-namely, that it is a more luxurious habit, a more
which he introduces to our norice in his letter on Mr. Howorth vigorous health, a less precarious existence, induced by the care
(NATURE, July 6, 1871, p. 181). In this case the hideousness of and attention of domesticators, that have caused the sterility : tire coinage is some guarantee against its reception. that these animals are too well off, and not that they are ill off
Malvern Wells, July 8
C. M. INGLEBY in any way; and this theory explains the whole most conclusively. On the o her hand, and in opposition to this vast and uniform collection of examples, Mr. Darwin adıluces a few instances
Affinities of the Sponges which tell the other way, but they are very few in number, and seem to me explicable on other grounds. Ferrets, it is notorious, I HAVE just read with much interest the paper in Nature by are always kept in a state of extreme depletion and as thin as Mr. W. Saville Kent, criticising my friend Carter's article in the possible. Domestic poultry are fed almost entirely on poor vegetable “Annals of Natural History” for this month, in which I sully food, while their wild and semi-wild relatives feed much more on
How Mr. Carter can have fallen into such an error, for worms, insects, and on animal diet generally. In regard to sheep, such I must call it, I cannot imagine, as comparing a group of it is notorious that very weak ewes generally bear twins, that animals in Botryllus to those sponge cells, even in so highly a Somersets and Dorsets are more fertile than Southdowns and developed form as Grantia. For, taking this as the highest known Leicesters. We have, I may add, no facts to guide us in form of sponge animal, it is at most only a monociliated sac, as regard to wild dogs, and few in regard to wild cats, but we do shown both by Prof. Clark and by Mr. Čarter. Now, it is well know that in tame ones the hall-fed lantern-ribbed curs are more known to all investigators, and Mr. Carter has shown it himself, prolific than their sleek relations. In regard to domestic fowls, that the animals of Botryllus have distinct oral and fæcal aperand especially pigeons, we must remember that their condition is tures, whereas the sponge cell, so far as has yet been seen, has materially altered by the disuse or only very partial and irregular only an oral aperture. Again, the Ascidian Botryllus is shown use of their powers of flight, this must reduce their circulation to be far higher in the scale when we come to compare its and vigour very considerably, and make them pro tanto so much internal organisation, and not merely to confine ourselves to weaker. But these instances, upon which Mr. Darwin relies to the sac-like tunic. The discharge of the fæcal matter into a answer Doubleday and others, are very partial indeed. In his common cloacal canal is to me not a sufficient reason for comown pages, as I have already said, they form a very small paring these groups of animals to the sponge animals in Grantia. element compared with the overwhelming cases he quotes on the But what I wish to draw attention to more particularly is this, other side. So much so, indeed, that these cases may be taken that in the hurry and bustle of our investigators of the present as exceptions which prove the rule that domestication and im- day, all old associations are mostly, if not entirely, forgotten. I proved conditions of life induce sterility in animals.
can scarcely think that they are ignored, but are forgotten. It savours of scholastic philosophy to speak of Nature as Thus, Prof. Grant was, I believe, the first to determine the exercising any influence on the regeneration of races, and yet character and the full importance of the seed-like body in there may be sound philosophy in the old notion that when Halichondria by placing watch-glasses in the vessel in an individual or a class is in danger of being extinguished which living specimens of the above sponge was placed ; the from want, Nature puts forward a special effort to preserve bodies were thus discharged from the fæcal canal of the parent it. The sickly mother, the half-starved plant, is more likely to sponge, and attached themselves to the watch-glasses, and he then breed than the healthy and the vigorous. If we remove the carefully watched their development. Mr. Carter, being a pupil of peasant's family to the drawing room, it will cease to be com. Dr. Grant, no doubt followed his teacher's plan of investigation, posed of ten and twelve children. If we remove our daisies and which has led to the brilliant results of this gentleman's in
vestigations of the fresh-water species in the tanks at Bombay.
The Late Thunderstorm The clear and lucid manner of investigation detailed by Prof. An ash tree in the garden attached to the farmhouse of Wester Grant in the Edinburgh New Philosophical Journal (1826-27) | Cringate, near Fintry, struck by lightning on the 20th of June, might be held as a pattern for investigators, but he appears to be presents a singular appearance. almost entirely lost sight of.
About 20ft. from the ground a large branch has been torn from Again, as regards the animals of Grantia compressa, Prof. the trunk. The bark has been neatly peeled off for a few feet Reay Greene certainly preceded both Prof. Clark and Mr. above and below the place from which the branch shot out. The Carter in his investigations, and has figured these monociliated wood has been first struck a little above the branch, and shows a animals in his handbook, published in 1859, p. 31, fig. 6. The clean cut, such as might have been made by a sharp-edged tool, figures are on the same scale as those given by Mr. Carter, and as if a chisel three inches broad had been driven into the wood indeed some of the groups figured are so much like those given by for about four inches. The branch itself has been torn, not cut, Mr. Carter in the “ Annals,” pl. 1, sqr. 13, a, g, h, that it and a stripe of the trunk about two feet long below the branch would be difficult to separate them, and the same may be said of has also been torn out. Fig. 41 of Prof. Clark's in "Ann. Nat. Hist.” pl. 6, 1868. For the next four or five feet the tree has suffered no damage The only difference being the want of the funnel-shaped mouth, of any kind, but after that space the trunk bears six parallel which seems to have escaped the observation of Prof. Greene, downward scars, varying in length from two to five feet. The probably owing to want of definition in the instrument used in scars do not all begin or end at the same height, although each the investigation. Now there is an amount of credit due to the might be cut in some point by a horizontal plane passing through first demonstrator of these animals, which, so far as I have seen, the tree. They spread over about half the circumference of the does not appear to have been accorded to him ; and I therefore trunk, and can all, or nearly all, be seen from one standpoint. take the liberty of directing attention to this fact. I do not The most striking circumstance, however, is the almost perknow Prof. Greene, and therefore do not take up this matter on fect parallelism of the scars, which are not vertical, but a little personal grounds, but only in fairness due from one scientific twisted round the trunk like the rifling of an Armstrong gun, man to another, and I hope my friend Carter will take this in the the rifling in this case being on the outside of the barrel. Six spirit it is intended.
EDWARD PARFITT chisels of about half an inch in breadth seem to have ploughed Exeler, July 8
into the wood, tearing off at the same time rather broader stripes of the bark. Towards their lower ends the three right-hand
scars cease to be quite parallel, and tend to converge ; but all Cramming for Examinations
three die out before the convergence takes place, and the tree
for the next two seet or so is unscathed. Five feet from the I ENCLOSE one or two bona fide extracts from “Middle Class”
ground (at about the point at which the three scars would con. examination papers which have during the past few weeks come verge, if produced) a single rut cutting deeply into the wood under my notice officially.
commences, which continues down to the soil. I do not wish thereby to reflect so much on the candi- The garden wall (which is a “dry-stone dyke," i.e. of loose dates as upon the mode of teaching in Middle Class schools, uncemented stones) passes some three feet behind the tree, on which produces such results.
the side directly opposite to that on which the markings above As might be expected, where evidence of "cramming" from a described occur. Outside of this garden the lightning has text-book and want of practical knowledge are equally manifest, | ploughed two pretty deep parallel ruts through the grassy soil some of the answers in the papers from which these are selected
some four feet apart, and stretching from the foot of the wall to are pretty good—but what can be the real value of knowledge of the edge of a ditch, a distance of three feet. These ruts are this sort ?
the last observable traces of the passage of the lightning, and The questions are sufficiently indicated by the answers. were probably made by the currents which engraved the three
left-hand scars on the tree. CANDIDATE A.
Of course it is impossible to decide
whether the currents passed through the open wall, or down the Chlorine may be taken from decayed vegetable matter and
outside of it. animal matter, also manure.
It is used for killing
Three sheep on the neighbouring farm of Spittalhill were killed insects, it is compounded with lime, and is very good when
in the same thunderstorm. Their carcases were found lying in a compounded with lime for the manuring of fields. Lime is chiefly line and were very much swollen, but bore no external marks of formed from Chlorine.
injury. A small patch of wool had been stripped from the flank
of one of them, but probably this had no connection with the CANDIDATE B. cause of death.
R. L. JACK Chlorine is prepared by mixing Ca Cl, with H,O
Geological Survey, Fintry by Glasgow, July 5
As you have favoured my work on "Saturn's Rings and the
Sun with criticism, I feel sure that as that criticism is adverse CANDIDATE C.
to my views, you will in fairness allow me to reply to it. Carbon is an elementary substance, it is one of the consti
I will do so in detail. Your reviewer commences very much tuents of the atmosphere, it is found in lime and pits among the
under the impression that Prof. Clerk Maxwell having investi. coal. When the lime is soaked with water the carbon escapes gated the “ Stability of Saturn's Rings," no one else is to ven. out and the lime moulds away.
ture into any discussion touching on their nature or origin. In AN EXAMINER
fact he issues a caveat-Prof. Clerk Maxwell has concluded the subject! Next he asserts that I have not seen the Professor's
work, because I ascribe to the perusal of Mr. Proctor's “ Saturn Great Heat in Iceland during the present Summer
and its System," the enlistment of my “interest in favour of the
Satellite Theory." This is surely beyond his province, as I am MR. R. M. Smith has received a note from Dr. Hjaltelin, free to choose my own point of starting. Mr. Proctor's work Corresponding Member of the Scottish Meteorological Society at interested me, and so did Mr. Clerk Maxwell's, but the former Reykjavik, dated June 30, of which the following is an elicited my work, the latter did not. extract :
He next accuses me of placing too great faith in figures, and “We have now the most excellent season you can imagine in shows surprise at my giving the hourly rate of the solar motion these latitudes, the average temperature for this month (June) to a mile, and the solar parallax to four places of decima's. being as high as 59°, hich is 12° higher than the mean tempera- The solar motion is that given by the Herschels, and the solar ture of the past four Junes. I was yes'erday near the Hengil | parallax by several observers. He is hard to please. But my Mountain, just at that place where we pitched our tent last time reviewer has unfortunately missed the point of my arguments. you were here, and the heat was quite unsupportable in the The actual velocity of this solar motion is perfectly immaterial ; valleys. The wind has been continually blowing from the south- indeed, had he followed the reasoning, he would have seen how west. Some Englishmen setting out for the Geyser will have pointless are his objections. something to tell of the extraordinary heat we have at present." As regards my arguments in favour of the meteoric theory of
ALEXANDER BUCHAN the sun, the reviewer is equally inaccurate. As to my being
July 13, 1871)
blindly enraptured with that theory, as he is pleased to state, I the white bellies of the porpoises. One looks down from
sharply defined as it is possible to imagine, and indicating phenomena.
the existence of coral beds or reefs just below.
Bellary, Madras Presidency Lastly, he culminates by saying I am “either innocently or wilfully ignorant of the palpably cyclonic appearance which spots [We give the passages referred to from Prof. Tyndall's frequently present." All I can say in answer to this is that,
lecture. -Ed.) having observed sun-spots myself for many years, probably as often as the reviewer, I have never observed one single appear- “Let us clear our way by a tew experiments towards an exance of a cyclonic nature. As I possess Mr. Carrington's valuable planation of the dark hue of the deep ocean.
Colour, you work, I have again referred to it, and find it in agreement with know, resides in white light, appearing generally when any conthe assertion in my book and my own observation.
stituent of the white light is withdrawn. Here is a liquid which apologise for my lengthy letter.
A. M. DAVIES colours a beam sent through it purple, and this colour is im2, Gloucester Terrace, Sandgate, July 4
mediately accounted for by the action of the solution on a spectrum. It cuts out the yellow and green, and allows red and blue
to pass through. The blending of these two colours produces On an Error in Regnault's Calculation of the Heat Con- the purple. Does the liquid allow absolutely free passage to the verted into Work in the Steam Engine
red and blue? No. It enfeebles the whole spectrum, but attacks IN Watts's “Dictionary of Chemistry” (vol. iii. p. 125), in with special energy the yellow and green colours. By increasing the article on Heat by Prof. G. C. Foster, it appears to me that
the thickness of the stratum traversed by the beam, we cut off an important error has crept into the discussion of the above cal- the whole of the spectrum. Through the deeper layer, which I culation.
now place in the path of the beam, no colour can pass. Here, The nature of the calculation is as follows :-A unit weight of again, is a blue liquid. Why is it blue ? Its action on the saturated steam at the temperature of 152°C, contains 653 units of spectrum answers the question. It first extinguishes the red ; heat. Suppose we allow the steam to expand and to do work then as the thickness augments it attacks the orange, yellow, and until the temperature falls to 503°C. the steam then contains 621 green in succession; the blue alone finally remains, but everyunits or 32 units less than before, hence starting with water at o°C., thing might be extinguished by a sufficient depth of the liquid. we give it 653 units of heat, and of this 32 only are converted “And now we are prepared for a concentrated but tolerably cominto work, giving us the fraction as the amount of heat con. plete statement of the action of sea water upon light, to which it verted into work; but the real work produced by an engine is owes its blackness. Here is our spectrum." This embraces three more than twice this. This difference in theory and practice is classes of rays—the thermal, the visual, and the chemical. These accounted for by the fact that saturated steam, in expanding and
divisions overlap each other ; the thermal rays are in part visual, doing work, is partly condensed, hence the body with which we the visual rays in part chemical, and vice versa. The vast body have to deal at the lower temperature is not all steam, but partly of thermal rays is here beyond the red and invisible. They are condensed water, therefore, does not contain so much heat as was attacked with exceeding energy by water. They are absorbed allowed it.
close to the surface of the sea, and are the great agents in evapoThis explanation is so intelligible as to be at first sight suffi- ration. At the same time the whole spectrum. suffers enfeeble. cient to account for the whole difference ; there is, however, ment; water attacks all its rays, but with different degrees of another cause, quite as important, and which is this; every time energy. Of the visual rays the red are attacked first, and first steam passes from the boiler to the cylinder it does work before extinguished. While the red is extinguishe:l, the remaining it is cut off, and allowed to expand ; this work is not done at the colours are enfeebled. As the solar beam plunges deeper into expense of the steam that passes into the cylinder, but of the the sea, orange follows red, yellow follows orange, green follows whole mass of steam in the cylinder and boiler, which expands yellow, and the various shades of blue, where the water is deep and is thereby cooled. The mass of water and steam in the enough, follow green. Absolute extinction of the solar beam boiler is, however, so large compared to that which passes into would be the consequence if the water were deep and uniform, the cylinder, that a thermometer could scarcely detect the cooling and contained no suspended matter. Such water would be as effect upon it, and before the next stroke this loss of temperature black as ink. A reflected glimmer of ordinary light would reach is made up by the fire. Though thus inappreciable, it is never- us from its surface, as it would from the surface of actual ink; theless very important, and in most engines would amount to but no light, hence no colour, would reach us from the body of one-third the work done ; in fact all the work done by the steam
the water. In very clear and very deep sea water this condition before it is cut off and allowed to expand is entirely neglected in is approximately fulfilled, and hence the extraordinary darkness this calculation, and a source of error introduced.
of such water. The indigo, to which I have already referred, is, To correct it there should be added to the heat in the steam at I believe, to be ascribed in part to the suspended matter, which the initial temperature, as many units of heat as the work done is never absent, even in the purest natural water, and in part to before the steam is cut off, would, if converted into heat, raise the slight reflection of the light from the limiting surfaces of strata the amount of water which passes at every stroke in the form of of different densities. A modicum of light is thus thrown back steam into the cylinder.
A. W. BICKERTON to the eye, before the depth necessary to absolute extinction has Hartley Institution, Southampton, June 26
been attained. An effect precisely similar occurs under the moraines of the Swiss glaciers. The ice here is exceptionally compact, and owing to the absence of the internal scattering common
in bubbled ice, the light plunges into the mass, is extinguished, THE CAUSES OF THE COLOURS OF THE SEA * and the perfectly clear ice presents an appearance of pitchy
blackness. PROF, TYNDALL, in his article in the Fortnightly “The green colour of the sea when it contains matter in a state
Review for the 1st of March, attributes the green- of mechanical suspension has now to be accounted for; and here, ness of the sea to the matter which it holds in solution. again, let us fall back upon the sure basis of experiment. This Perhaps the following may corroborate his theory. About white plate was once a complete dinner-plate, very thick and the Andaman Islands, where the sea is of the deepest strong. It is, you see, surrounded securely by cord, and to it a blue, there are most startling and sharply-defined changes lead weight is fastened. Forty or fifty yards of strong hempen of colour, from bright blue to green, where a bed of coral line were attached to the plate. With it in his hand, my assistant, exists. This coral is white out of the water, what its Thorogood, occupied a boat fastened as usual to the davits of colour when growing may be I know not, but the change
* A note written to me the 22nd of October, by my friend Canon Kingsley, I mention appears to corroborate the remarks in the contains the following reference to this point: -"I have never seen the Lake article in question, which are appended below, about the
of Geneva, but I thought of the brilliant, dazzling dark blue of the mid At
lantic under the sunlight, and its black blue under-cloud, both so solid that green hues observed upon the plate, the screw blades, and one might leap off the sponson on to it without fear ; this was to me the most
wonderful thing which I saw on my voyage to and from the West Indies." * Communicated by Prof. Tyndall.