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said :

therefore no free affinities”? This example shows that THE TRAVELS OF A PAINTER OF FLOWERS. the paragraph quoted above from p. 76 is much too dogmatic.

Recollections of a Happy Life, being the Autobiography I do most strongly object to such a statement as that

of Marianne North. Edited by her sister, Mrs. John on p. 69, where, speaking of carbon monoxide, it is

Addington Symonds. In Two Volumes. (London :

Macmillan and Co., 1892.) cm The molecule of this compound is represented by the Most of the readers of Nature will know without formula

telling that Marianne North was a world-wide *C||0.

trave ller, that she travelled in pursuit of nature, that she

was an accomplished and faithful painter of plant and Here the asterisks are intended to show that two affini- animal life, and that the results of a life's labour were ties are unsaturated ; this is proved by the fact that the presented by her to the nation, and now cover the walls compound unites with two atoms of chlorine, forming of a building in Kew Gardens, erected at her expense phosgene gas, ci

Most persons, too, who knew; her personally-and her C=0."

acquaintances and friends are as numerous as her travels CI

were wide-will be glad to know something more of her What is proved by the fact of combination with her impressions of peoples, of places, and, above all, her

history, and especially something more of her travels, of chlorine? No one can attach any clear meaning to the impressions of the plant and animal life of the many statement “two affinities are unsaturated.” The only countries she visited and to which she gave her life. All practical meaning these words have is, “The molecule who had the pleasure of knowing her personally will CO can unite with two other atoms of certain kinds”; remember her stately presence, her kind face, her charmthat is to say, the sentence quoted, when put into the speech of the plain man, asserts that the fact that co ing manner, and her entertaining conversational powers

--now relating the difficulties and delights of her expedoes unite with 2Cl proves that CO can unite with 2CI. The later paragraphs, treating of the physical properties comforts and genial society. She wrote as she talked,

riences in foreign lands, now her appreciation of home of bodies and the connexions between these and the constitutions of the same bodies, seem to me to be both very her book in the same style.

and she was a fertile letter-writer; and she has written well done and very disappointing. They are well done because an earnest attempt is made to put the matter Europe, and also went up the Nile and visited Syria, and

In early life Miss North made various journeys in clearly, but they are disappointing because it is quite im- painted many flowers ; but with the exception of the Sicipossible to grapple with these very difficult matters in the lian Papyrus, and perhaps two or three other little pieces, space which is given to them in this book. I do not think that anyone will succeed in getting a grasp of Raoult's law pages of her book are devoted to her early life, and it prac

none of this early work is in the gallery at Kew. Only 38 from the pages which are grouped around paragraph 133. The application of Raoult's law to determine molecular tically begins with her more distant travels; the first long weights, given on p. 137, is based on the constant 62, trip being to Canada and the United States, and extended which has been shown by van 't Hoff and others to be later she started for Brazil, where she made a long stay,

to Jarnaica, whence she returned to England. Two months erroneous. But it is much easier to find fault than to compose such

and then returned direct to England. The next journey a book as this. A careful perusal of the work leaves the and Java, and then home again

. Her paintings attracted

included Teneriffe, California, Japan, Singapore, Borneo, impression on my mind that, as a synopsis and suggestive remembrancer to the student who knows general chemistry attention, and she complied with a request to exhibit

some 500 of them at Kensington. This matter being well, this book will prove useful, but that it is too condensed and too slight to be of much service to him who is arranged, she proceeded to India, landing on the way at beginning the study of general chemistry. Most of the Lisbon, Gibraltar, Malta, and Galle; and India was subjects dealt with cannot be made clear except by going traversed almost from east to west and north to south.

The narrative of this journey is perhaps the most ininto details, and illustrating them with considerable profusion. When one attempts to deal with these matters in teresting part of the whole work. On her return home a broad and general way, and at the same time to devote there was an exhibition of the accumulated paintings in only a few pages to each section, one is almost obliged Conduit Street ; and a visit to Mr. Darwin, which ended either to make statements so generalized that they are of in a determination to go to Australia and paint the

It should be very little use to the earnest student, or only to touch the flowers of the fifth quarter of the globe. fringe of each part of the subject. Chemistry is an abstract mentioned that in the meantime Miss North had adopted science to a much less degree than physics ; hence such a suggestion of the Pall Mall Gazette that her paintings

should find their home at Kew, and her generous offer short statements as those which sum up and include in themselves whole provinces of physical knowledge cannot

was accepted. So it was, that when Darwin told her yet be made in chemistry. Where the “ Outlines of Theo that her collection of paintings would be an imperfect retical Chemistry” fails for the most part it fails because representation of the vegetation of the world without the no book could succeed ; it fails because it attempts to do Australian element, she took it as a “royal command,” that which cannot, at present, be done.

and prepared to go forthwith. This journey some of the

old scenes were revisited, brief halts being made at Galle M. M. PATTISON MUIR. and Singapore, a longer stay with the Rajah and Rani

Brooke in Borneo, and thence to Queensland. New South The foregoing is an outline of her journeyings, but the Wales, Victoria, West Australia, Tasmania, and New book sbould be got for the details, which are almost Zealand were successively visited ; but incessant travel- always interesting, often clever and quaint. Here and there ling, climatal changes, and continuous work had begun one meets with uncompromising criticisms and descripto tell on the constitution of this brave woman, who tions of persons that might have been expunged with suffered much in the colder regions. Now, the great advantage. The descriptions of the vegetation of various object was to make the collection of paintings as complete regions, with particulars of the principal elements, are as possible, and she spared neither her pocket nor her pleasant and instructive, often containing much original person in trying to carry it out. Her book is so essentially information ; and will be greatly appreciated by those the history of her gallery at Kew that one cannot dis who frequent the gallery at Kew, of which the book, as sociate them. The Australian journey was fruitful beyond already stated, contains the history. all others, and the Australasian section of the gallery is After completing her work at Kew, Miss North took an perhaps the most attractive of all, being a marvellously old-fashioned house at Alderley, in Gloucestershire, where complete representation of the varied and curious flora she formed a charming garden ; but her constitution was of that region. The homeward route was across the broken, her suffe rings increased, and she died in August Pacific, calling at Honolulu, landing at San Francisco, 1890.

W. B. H. and off at once to the redwood and mammoth-tree forests for more painting. Then across America by the southern route, and back to old haunts in the North-Eastern States,

AMERICAN TOWN TREES. and home again to open the gallery, which had been built during this journey. Hanging the pictures was a

Our Trees. By John Robinson. (Salem : Horton and most laborious task, from which Miss North took no rest.

Son, 1891.) At this time the writer first made her acquaintance, and

"HIS short account of the trees of an American town

THIS was engaged by her to botanize the paintings and com

and its neighbourhood consists of reprints of pile a popular instructive catalogue. This occupied two newspaper articles written in 1890-91 for the benefit of or three months; and most interesting work it was, usually local readers : they have been re-compiled into book form brightened by her presence.

at the request of the directors of the Essex Institute, and No sooner was the opening of the gallery accomplished, date from the Peabody Academy of Science, Salem. than the terribly jaded donor of this munificent gift to Several points strike a careful reader of the book. the public began to think of visiting new regions to The writer draws special attention to the fact that the further enrich it. But I must be brief, for even to articles, or chapters, are not intended as botanical essays ; catalogue these journeys occupies much space. South and the reader will probably decide that the remark was Africa was next visited, and several months' uninterrupted unnecessary, for a more unscientific work dealing with a work, much of it done under trying conditions of failing scientific subject would be difficult to find; but there is a health, yielded so bountifully that it was determined to peculiar charm in a certain style of talks about natural build a wing to the gallery, for the existing walls were objects—for instance, in some of the more chatty paraalready completely covered.

graphs of White's “ Selborne," or Walton's “ Angler," and Miss North intended going from South Africa to Mada- even Evelyn's “ Flora "—which attracts the most devoted gascar, but the means of communication were irregular student to refreshing looks around his subject matter and uncertain, and her health so bad that she returned from every-day points of view, and this little work home; but having to some extent recovered, she went the possesses that charm. Few facts of scientific importance following year (1883) to the Seychelles, to paint the beauti- are met with in such writings, and still fewer of the ful palms and screw pines of those islands. Even this did generalizations which make science what it is: the not satisfy her, and she started on her last journey in specialist may even deride the writing as “talkeeNovember 1884. Chili was her goal, and the principal talkee"-gossip, if you will ; and even the broadest object of this long journey was to paint the Araucaria thinker may be inclined to wonder why such articles imbricata in its home, as she had already painted the are written ; all this, and more, may be true, and yetBrazilian and Australian species. She also succeeded in there is the charm, nevertheless, and it is very apt to painting a considerable number of the characteristic seem appropriate where trees and flowers are concerned. types of the vegetation of that country. But this voyage, Whether it is advisable that such writings should increase by way of the Straits of Magellan, tried her waning is a matter likely to settle itself, simply and certainly, strength very much, and a less energetic person would because very few can produce them. A scientific work, have collapsed entirely. In the last chapter of her “Re- then, this is decidedly not. It is a series of homely collections” we read that all was enjoyment until they chats about trees, by one who knows and loves them. reached Bordeaux. “Then my nerves gave way again The latter fact leads to another-namely, that such a (if they were nerves), and the torture has continued more writer cannot help telling you something worth learning or less ever since.” Beautiful Rio was touched on the even though it be by the way, and merely incidental. outward voyage, and on the homeward route, by Panama, In the first place we gather some ideas as to what trees old friends were looked up in Jamaica. England was are common in the streets and gardens of a Massachusetts reached in the spring, and it cost another year to re- town, and the evidently thriving condition of magnolias, arrange the gallery ; the introduction of the South African, sumachs, maples, witchhazels, mulberries, hickories, Seychelles, and Chilian paintings entailing renumbering gingkos, catalpas, sassafras, and many other beautiful throughout, in order to preserve the geographical order. trees, makes envious one who knows what difficulties are met with in this country in attempts to rear even present. Once more we have specific gravity observations in able “ specimens" of such favourites in our smoke- which corrections for temperature and air displacement beladen and crowded cities and suburbs.

are ignored ; and although the author attempts to set Then, again, the English reader gathers some informa- density and specific gravity, it is questionable if he suc

right the prevalent misconception as to the meaning of tion as to the Western popular names of trees, well known ceeds. According to him, specific gravity is always to him by very different ones; how many English people relative; it is the same magnitude as relative density. know what are the "cucumber-tree,” the “yulan,” the The use of absolute specific gravity-or, shortly, specific " buckeye,” the “ butter-nut," and the " button wood”? gravity with no temperatures of comparison attached-as Bits of history also occur, and incidental notes on the from a physical point of view, the definition of the

denoting the weight of unit volume, is here overlooked. rates of growth of various trees, their ages, &c. So that, absolute density of a gas as the mass of 11'16 litres is after all, there are some dry facts in this singularly quaint a needless complication. In ascertaining the percentage and simply written talk about trees. We must not claim composition of a compound it is insisted that, first of all

, much for the work in this respect, however ; and perhaps the molecular weight must be calculated. The examples the chief reason we like the writing is because of its con- Basic lead chromate, &c. The student is thus led to

given to illustrate the rule include apatite, apophyllite, trast to the empty and inflated style of too many of our infer, here as elsewhere in the book, that the molecular native newspaper articles on similar subjects.

weights of such bodies can be fixed.

The freezing-point and boiling-point methods of ob

taining molecular weights are disposed of in two pages. OUR BOOK SHELF.

No hint is given that the solutions must be dilute and Synopsis of Non-Metallic Chemistry. By William Briggs, non-electrolytic, if consistent results are to be obtained; B.A., F.C.S. Pp. 90. (London: W. B. Clive and these methods is still subject to difference of opinion.

or that, in general, the interpretation of the results of Co.)

It is erroneous to state that “the alteration in the This book is intended for students preparing for the volume of a gas is proportional to the so-called absolute Matriculation Examination of London University. After temperature,” or to speak of “ Dalton and Henry's law." the contents of an ordinary text-book have been studied, Henry's law is distinct from Dalton's, and is the older by the reader is here supposed to find the more important two years. points which have to be remembered, and which serve We have dwelt on some of the points which seem to to recall the less important. Interleaved note-paper call for criticism. On the other hand, the book has its is provided, whereon facts readily forgotten may be good features. The problems are numerous, carefully recorded.

selected, and well arranged. Contents, answers, and As is usually the case with such cram-books, little can index are supplied. It seems to us, however, that, be said in favour of the quality of the information instead of being as good as several of its kind already supplied.

in existence, it, as a new book, should have been better. Formulæ are stated to be "arrangements of letters representing a molecule of a compound,” and this defini

The Year-book of Science. Edited for 1891 by Prof. T. tion is illustrated by regarding Fe,0, as denoting a

G. Bonney, D.Sc., LL.D., F.R.S. (London : Cassell molecule. The vapour-density of hydrofluoric acid is

and Co., 1892.) given as 10, and the solubility of hydrogen in water as All who have any sympathy with scientific pursuits will

practically the same at all temperatures from 1° to 20°”: heartily welcome the appearance of this epitome of the neither statement is up to date. Such antiquated terms more important results of the investigations which were as basylous and chlorous, which are freely employed, published during the past year. Scientific inquiry now might well be replaced ; and to speak of distilling potas- covers so much ground that all men of science must be sium perchlorate with strong sulphuric acid is inaccurate. more or less specialists, and it is difficult for them to The account given of fractional distillation is worthy of keep in touch with the developments in other branches reproduction. The mixture of liquids is heated “up to through the usual channels, although it frequently the lowest of the boiling-points of the liquids present. happens that an advance in one subject may throw light The whole of that liquid (?) will be converted into vapour, upon and induce investigations in another. There are and can be condensed in the usual way. On heating thé also many engaged in practical pursuits who require a remaining liquid up to the next boiling-point, we can convenient means of determining how far contemporary separate another of the constituents, and so on until they researches may be technically applied. are all separated out. The different liquids thus obtained With a well selected staff of contributors, the editor has must be redistilled to get them quite free from the others, attempted to meet the wants of all by the present volume, small quantities of which may have been distilled over in which is divested as far as possible of technicalities. The the first process."

scope of the work is sufficiently defined by the following This last extract is typical of the bulk of the knowledge paragraph from the editorial : contained in the book, which, to say the least, savours " It is almost needless to remark that this volume is more of the class-room than the laboratory.

not intended to be a record or catalogue of papers. The A table of contents, a glossary, and three appendixes endeavour of its projectors and compilers has been to are provided. The last are concerned with the prepara- select those memoirs, in each several department, which tion and purification of substances and with the simpler appeared to be of somewhat exceptional interest, either chemical calculations. A list, with answers, of numerical by throwing light on special difficulties or by being examples set at the matriculation examinations is in- suggestive of further advances." cluded.

In a work of this kind strict impartiality is essential,

and we see no reason to suppose that the various conChemical Calculations. By R. Lloyd Whiteley, F.I.C. With a Preface by Prof. F. Clowes, D.Sc., F.I.C. whole, the production is very satisfactory, and the im

tributors have abused the power vested in them. On the (London: Longmans, Green, and Co., 1892.)

provements which the editor contemplates for the next This is still another addition to the numerous manuals volume will make it more so. One can only wonder that on chemical arithmetic, and the points wherein it differs science has had to wait so long for a year-book of its from its predecessors are somewhat difficult to discover.

Own,

Handy Atlas of Modern Geography. (London : Edward Let me first acknowledge the courteous tone of Mr. Hopkins's Stanford, 1892.)

letter, and express my sense of the value to myself of It would be difficult to obtain a small atlas more com

criticism from his pen, and the more so since I have been plete than this. Every place of any importance appears

labouring under the disadvantage of being practically entirely

uncriticized so far-a disadvantage that I have not failed to to be represented on one or more of the thirty coloured

appreciate. maps. The degrees of latitude and longitude are sub

Now, Mr. Hopkins remarks : "Mr. Coste's experiments are divided into parts of five minutes each, so that the very useful as forming a method of classifying these pigments; positions of places, the names of which are not engraved, but . : . they are of far too empirical a nature for any concan be easily and accurately located by reference to the siderations as to the constitution of the bodies to be based upon alphabetical list at the end. This list is a comprehensive them.” one. It gives the latitude and longitude of the principal Here it is that Mr. Hopkins appears to have missed the point mountains, rivers, capes, bays, islands, towns, and villages, of my work. If he will do me the favour to refer to the and forms an excellent supplement to a very good atlas.

detailed account of my experiments in the Entomologist, passim, I think that he will find it tolerably clearly emphasized that my interest in this work, so far, has been almost entirely biological.

I stated expressly in my opening article that my object had LETTERS TO THE EDITOR.

been to discover, if possible, the genealogies of the colours, and (The Editor does not hold himself responsible for opinions ex

to obtain evidence (so far as coloric characters could afford it) pressed by his correspondents. Neither can he undertake of the phylogenetic relations of allied species : and I may perhaps to return, or to correspond with the writers of rejected varieties of whose occurrence in the natural state I have since

add that the results obtained have enabled me to predict several manuscripts intended for this or any other part of NATURE. No notice is taken of anonymous communications.]

been informed. So that Mr. Hopkins is miidly reproaching

me because my work does not tend in a direction at which it was Aurora,

not originally aimed, while he is at the same time good enough A VERY brilliant display of aurora was seen here last night,

to admit that it is of some use for the end at which it was aimed. the 25th inst. At about 9:25 p.m. a number of red streamers However, it was only to be anticipated that one could not go proceeded from a length of some 110° in azimuth along the very far without becoming involved in the further question as northern horizon, and extended upwards for (on an average) 30°. to the constitution of the pigments; but here I was met by The length of the streamers varied quickly, sometimes shooting three considerations. In the first place, I was anxious to obtain upwards for 70° from the horizon. In the course of five first of all as much as possible of what Mr. Hopkins designates minutes the red streamers gave way to white or yellowish white empirical” evidence as to the reactions and classification of ones, narrower and more sharply defined than the red ones. the pigments besore making any researches at all into their conAt 9.40 p.m. there was a decrease in the brilliancy of the stitution ; secondly, the amount of material at my command was phenomenon, but at 9.45 p.m. long red streamers again far too scanty for any even approximate analysis ; and in the appeared for a few minutes, which again shortly gave way to a

third place, shortly after my experiments had been commenced, brightness of the horizon only. Close to the horizon the colour my attention was drawn to an abstract of a paper by Mr. was white, or nearly so, the whole time. The apparent point Hopkins on the constitution of the yellow pigments. Finding of convergence of the streamers was far south of the zenith, say that he was already in possession of the field here, I felt almost 30°

Geo. M. SEABROKE. bound to leave this part of the subject alone, at least for the Temple Observatory, Rugby, April 26.

present ; and I think that I may say that I have on the whole iaken exaggerated care not to extend my experiments into that

quarter where Mr. Hopkins was engaged, or to avail myself of PROBABLY many of your readers witnessed the brilliant dis- The discoveries that he had already made, in order to trespass play of the northern lights between nine and twelve o'clock last on his investigations. Putting aside my provisional suggestions night, the 25th, but it may be as well to call attention to it, as as to the nature of the "reversion effect,” it has only been at a being the finest display seen here for many years. Appearing comparatively recent stage of my work, and in consequence of soon after nine o'clock, the luminous arc and the radiating beams, experiments ihat have not yet been published, that I have at all sometimes rose and orange coloured, presented a varied and turned my attention to the constitution of the pigments; beautiful spectacle until close upon midnight, when they these results being such as would have compelled me to consider

the question even had I heard nothing of Mr. Hopkins's work. The most noteworthy features of this display were the vivid. I hope that this explanation will put me right in Mr. Hopkins's ness and height of the arc, which reached an angle of about 13° eyes, and will satisfy him that he has considerably misunder. above the horizon, whilst the beams were visible up to 51°. The stood the spirit of "some remarks [perhaps clumsily expressed whole expanse of the arc from east to west was about 93o, by me) made at the close of the last article"; and that it will and the duration of the phenomenon a little under three hours. also satisfy him as to the question of priority. I had no thought

ARTHUR MARSHALL. of questioning Mr. Hopkins's priority in his own work, and the Cauldon Place, Long Row, Nottingham.

less so since I have throughout been under the impression that

working mainly on different--though sometimes

adjacent-lines. A FAIRLY distinct aurora was visible here on the northern

I must not so far trespass upon your space as to criticize Mr. horizon last night. I first observed it at 9.15, when the Hopkins's criticisms upon the “reversion effect"; but I will streamers appeared somewhat less bright than the Milky Way. ask him kindly to examine the detailed accounts of the Ten minutes later one streamer, about 15° west of north,

"reversion " experiments which I gave in the Entomologist, brightened considerably, and appeared of a pale reddish-yellow since his remarks appear to me somewhat to ignore the evidence tint. It fluctuated in intensity, and soon became less bright. there brought forward : and at the same time I may remark that The streamers, which inclined slightly to the west of the vertical,

his statements as to the constitution of the yellow pigments extended to about 30° to 40° above the horizon.

appear to me hardly to invalidate, but rather indirectly to confirm, I watched them till 9.50, when they seemed fading in intensity,

the suggestions made by me as to the reversion reaction with red and when I looked again at 10.30 they had disappeared entirely. pigments. The new information that Mr. Hopkins promises in

ARTHUR E. BROWN.

his closing paragraph I shall look forward to with great interest. Thought Cot, Brentwood, April 26.

April 22.

F. H. PERRY COSTE.

faded away.

we were

Pigments of Lepidoptera.

I was about to pen some remarks on Mr. Perry Coste's recent The appearance of Mr. F. Gowland Hopkins's letter on this articles on this subject, when a letter from Mr. Gowland subject in the last issue of NATURE (p. 581) demands a brief Hopkins in the last number of Nature (p. 581) expressed explanation from me-although it is not easy to reply satis- substantially the same views as those which I had arrived at. factorily within narrow limits—and the more so since Mr. I write now rather to support Mr. Hopkins in his strictures Hopkins appears to have somewhat misunderstood my stand- than to offer any fresh criticisms of my own. The articles on point.

“Insect Colours” published in these columns are, as the author

is so.

states, to be regarded in the light of an abstract of a series of specimens sufficient to show students the ordinary types of the

The

fossil. more extended papers published in the Entomologist. papers in the latter publication from their title led us to suppose

As to the Laurentian age attributed to the Tudor beds, I have that Mr. Coste had made some contribution to our knowledge already explained that this I subsequently regarded as an error, of the chemistry of insect pigments. I read them from month

and so stated not long after the date of the paper of 1867. I to month in the hope of getting new light on this subject,

now regard them as less ancient, though of pre-Cambrian age. which is of such general interest to both chemists and

I shall be happy to show to anyone my little collection from biologists : I regret to say that I have been grievously detected the canal system ; but of these particular specimens I

Tudor and Madoc, including specimens in which Carpenter disappointed. The experiments thus far described amount simply to the fact not altogether astonishing — that have unfortunately no duplicates for distribution, and would strong chemical reagents modify the colours of Lepidop- prefer to exhibit the slices in the modes I have found best terous pigments or in some cases dissolve them out of the suited for the development of the structures ; as otherwise there wings. The bearing of these observations on the chemistry of might be some doubt whether the resulting impressions would the pigments is so remote as to be practically useless until we

more resemble Mr. Gregory's figures or Dr. Carpenter's. know something of the chemical nature of these pigments. The

Montreal, April 6.

J. WILLIAM DAWSON, methods adopted by Mr. Coste are not likely to advance our knowledge in this direction very much, and it is certainly re

The Theory of Solutions. markable that in treating of yellows he makes no reference 1 to the only real contribution to the chemistry of Lepidopterous the “gaseous laws" of solutions, there seem to exist no more

I am glad to see that as to the main point, the character of pigments, viz. the experiments made by Mr. Hopkins, and

differences between Mr. Rodger and me. For Mr. Rodger, in published in the Proceedings of the Chemical Society in 1889. Mr. Coste is no doubt acquainted with those South American

his letter on p. 487 of Nature, limits his remarks to some

dialectical expressions, to cover an honourable retreat. I wish Papilios with a large red 'spot on the hind wing, which spot

not to follow him on this way, because it is an endless one. loses its red colour and becomes of a brilliant metallic bluish

As to the application of van der Waals's formula on solutions, green when the wing is tilted so that the incident and reflected

Mr. Rodger is now forced to confess that this application is not rays form a very wide angle. The colour is in this case doubt.

so “meaningless " as he has formerly written ; but he asserts less a mixed result, partly due to pigment and partly to inter

that, shortly spoken, the form of application given in my book ference. Now, anyone who has observed this and other similar

To say the truth, if I have to choose, as in this case, colour phenomena in insects might describe his observations as contributions to the physics of insect colours. If he thought and the agreement of this same formula with experiment, I prefer

between the agreement of a formula with Mr. Rodger's opinion, proper to adopt this course, he would be misleading physicists.

the latter.

W. OSTWALD. The observation of the bare facts is as much a contribution to

Leipzig, April 12. the physics of insect colours as the statement that a rainbow can be seen in the sky is a contribution to the physics of illuminated

Physiological Action of Diminished Atmospheric water-drops. It seems to me that Mr. Coste's experiments bear

Pressure, the same relationship to the chemistry of insect colours that the mere observation of interference colours in insects bears to the

With reserence to the effect of diminished atmospheric physics of insect colours.

pressure on the vital powers, alluded to in Prof. Bonney's Quite independent of the facts recorded by Mr. Coste is the

review of Mr. Whymper's “ Travels among the Great Andes of interpretation which he puts upon them. Here I must de

the Equator” (NATURE, April 14, p. 561), I do not know cidedly express dissent. It cannot be admitted, because by the

whether it is worth while recalling the well-known fact that action of certain reagents green is changed into yellow or red

numerous passes in the Himalayas, ranging from 17,000 to into yellow, that this indicates the evolution of green or red

19,000 feet, are habitually traversed by the hillmen, in the from yellow. There is no evidence that this result is a reversion

summer, with their flocks of sheep and goats carrying borax, &c.

The highest pass is said to exceed 20,400 feet. In the same effect at all. The analogy between the action of strong acids in modifying the colour of an animal pigment and the effect of

mountains Messrs. Schlagintweit reached an altitude of about true reversion is forced, and has no parallel in natural pro

22, 200 feet (Proc. As. Soc. Bengal, January 1866), while Mr. W.

W. Graham ascended to 23,500 feet in 1883 (NATURE, September cesses. Hot water is a chemical reagent ; by its action on the brown pigment of the lobster the latter becomes red. If from

II, 1884). I have myself, on several occasions, been to elevations this observation I drew the inference that the ancestral lobster

of 17,000 to 19,000 feet, and beyond shortness of breath when was red, and that the hot water produced a reversion effect, I do climbing, never experienced any ill effects except once, when I,the not think that Mr. Coste would agree with me.

four plainsmen with me, and three out of a considerable number R. MELDOLA.

of hillmen, felt severe headache during the evening after crossing Oxford, April 24.

a high pass. My companion on one trip, however, almost invariably suffered very severely from mountain sickness under similar circumstances.

F. R. MALLET. Eozoon.

18, The Common, Ealing. MR. GREGORY has, I sear, slightly mistaken the meaning of my remarks, which were intended rather to excuse than to blame

Sensitive Water Jets. him. The specimen of Eozoon collected by the late Mr. Vennor at Tudor was figured in connection with my paper of

A FORM of this effect lately presented itself, which seemed in

some ways new. A thin jet, 5 feet high and arched so as to be 1867 as a type specimen, in so far as macroscopical characters are concerned ; but it does not follow that slices from specimens distance a small Wimshurst machine was set going : not

3 feet at the base, was falling in a feathery spray. At 13 feet less perfect in that respect, and now in my collection, may not instantly, but after two minutes, the spray gathered itself up be more instructive as showing minute structures. I may refer in this connection to the three specimens from Tudor and Madoc down and the machine was discharged the falling water would

almost into one clear line : although the jet was turned up and (Madoc being in the same formation with Tudor) figured by not resolve itself again into spray for fifteen or twenty minutes. Dr. Carpenter in our original paper in the Journal of the

It is difficult to imagine the medium for this action : it is too Geological Society, vol. xxiii., pl. xii., Fig. 1. If anyone will indefinite, perhaps, to suppose that an indicator is found for the take the trouble to compare these with the figures Mr.

trembling of a disturbed ether while it is dying down. Gregory's paper in the same Journal, vol. xvii., he will have a

The well-known experiment is not known enough, for it is not singular and impressive illustration of the different ways in

often described in books. Take a glass rod, electrified ever so which things supposed to be the same may appear to observers little, to a certain point ; at once the jet collects itself ; a slight of different types.

move away brings back the old disorder, while an inch nearer Mr. Gregory is in error in supposing that he could see in the

makes things much worse. It is a striking illustration to cases of the Peter Redpath Museum my specimens from Tudor and Madoc. I have not yet been able to place there any portion We can perhaps understand those thick thundery rain-drops,

help one to imagine what the electrical forces of the air may do of my microscopic cabinet of Eozoon ; but only a few hand

that almost allow us to pass between them while they are giving At least in NATURE : I have not the Entomologist at hand where I am

friendly warning of what will come.

W. B, CROFT. writing.

Winchester College, April 14.

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