=

being particularly elegant. On pp. 144, 145, in the proof of the important proposition that the ratio of any two rectangles R and R' is the same as that of the product of the height and base of the first, to the product of the height and base of the second, there are two, at any rate typographical, errors which would exceedingly trouble boys or the ordinary run of self-taught students. Also in a numerical example to this proposition the writer correctly gets R 4, and then says the first rectangle is 4 times R' greater than the second rectangle. On p. 148 the reasoning in theorem vi. is defective, and in the scholium there is a misprint; it is, however, not necessary to dwell fully on this Book V., which is especially faulty. We shall close our remarks on the text by quoting a sentence on p. 171, simply remarking that we could have extended our criticism to twice or thrice the dimensions of the present notice. The sentence is: "The further development of the Theory of Transversals is reserved for a special treatise on Modern Geometry, with a popular view of the recent improvements introduced by M. Chasles." May it be reserved to the Greek Calends! say

we.

Who and what is Mr. J. R. Morell, that he should venture to act as interpreter of M. Chasles' brilliant contributions to Geometry ? Such a work brought out by a competent writer would be of great use. It was in 1871, that Mr. Morell published "The Essentials of Geometry, Plane and Solid, as taught in French and German Schools, with Shorter Demonstrations than in Euclid," &c. After the reception this little work met with one would have hoped that the author would have learnt wisdom, and before he sent forth another such work into the world would have submitted it to one or two candid and competent geometrical friends. The book might yet be made a very fair one, but as it is at present we must condemn it most strongly.

There is an appendix of 205 exercises, and we have marked upwards of forty as each containing something objectionable in language or in geometry. We must content ourselves with a selection :- -30. Given a rectangle and a point situated in the interior of a quadrilateral; it should be" and a point within it" (or some such words; it is the billiard-table question which is given in many French text-books). 40. A triangle and any plane figure, in general movable in a plane, &c. 42. Which is the geometrical locus, &c. 103. A question of two concentric circles in the great circle, in the little one. : 116 is not neatly put; it is, "What is the geometrical locus of the centres of the circles which intersect orthogonally-that is, forming a right angle-two given circles?" 143, 193, he uses in the function, where an ordinary geometer would write in terms of. In such wise and in (for "into") frequently occur. Before closing our article, we must point out that the work we have examined is not to be confounded with "The Elements of Geometry in Eight Books; or, First Step in Applied Logic," by L. J. V. Gerard, which forms a volume in Dr. J. D. Morell's Advanced Series for Colleges and Schools. This is the work of an able and judicious writer; we must at present content ourselves with merely commending it to the notice of any of our readers interested in the subject. A word of praise we can extend to the external aspect of "Euclid Simplified;" it has a neat and geometrical design on the cover.

TISSANDIER'S PHOTOGRAPHY

A History and Handbook of Photography. Translated Edited by

from the French of Gaston Tissandier.

J. Thomson, F.R.G.S. (London: Sampson Low and Co., 1876.)

A1

LTHOUGH one may reasonably object to the statement made by an eminent French savant that 'chemistry is a French science," there is no denying the fact that photography, so far as its early history is concerned, is eminently a French art. M. Tissandier, the author of the work now before us, of course does not fail to impress this fact repeatedly upon his readers by speaking of photography as the "art of Daguerre," and indeed throughout the book he places his own countrymen in positions which might in some cases be justly considered as somewhat too prominent. The addition of some few historical notes, however, by Mr. Thomson, the editor, renders the work, on the whole, as fair a history of the subject as we could wish to read.

Of the three parts into which the book is divided the first is entirely historical, commencing with a description. of the camera obscura of Porta, and the discovery of "Luna Cornea" by Fabricius, and then proceeding to the early experiments of Prof. Charles, Wedgwood, Davy, and Watt. The connection of Daguerre with the first development of photography is of course known to all. The early life of Daguerre forms the subject of the second chapter, and the author here relates an incident which may be new to many of our readers.

It seems that in 1825 a poorly-dressed young man entered the shop of Charles Chevallier, which was at that time much frequented by amateurs, and demanded the price of one of the new cameras with converging meniscus lenses, which were then being made for the first time. The young man's manner showed that the price named was far above his means, and Chevallier then inquired for what purpose he required the camera. The stranger declared that he had succeeded in fixing the image of the camera on paper, but that the instrument he had employed was of rough construction, and he was anxious to continue his experiments with the improved apparatus. Chevallier being sceptical as to this statement, the young man placed on the counter before him a piece of paper, on which appeared a view of Paris, and on further questioning gave the optician a vial of blackish fluid, which he stated to be the liquid with which he operated. To continue, in the author's own words :-" The unknown explained to the optician how he should go to work; then he retired lamenting his hard fate, which would not permit him to possess that object of his dreams, a new camera! He promised to return, but disappeared for ever." It may be added that Chevallier could get no result with the liquid left with him. The incident was related to Daguerre, but the unknown inventor never appeared again, so that his name and fate remain a mystery. The succeeding chapters contain an account of the life and labours of Nicephore Niepce, and a history of the partnership entered into between this gentleman and M. Daguerre. Niepce's process, it will be remembered, depended upon the fact that "Bitumen of Judæa," when exposed to light, becomes insoluble in oil of lavender. Daguerre, continuing his researches under the

The history and progress of the new art of Daguerreotype is then traced, its purchase by the Government described, and the discovery of accelerating and fixing agents gone into. The editor at this stage reminds us that the use of sodium hyposulphite was first made known by Sir John Herschel, but Mr. Thomson erroneously terms this salt a "developing agent." We next arrive at that period of the history when the improvement in lenses effected by Chevallier enabled the time of exposure necessary for a Daguerreotype plate to be reduced, but even then the sitter had to remain motionless for four or five minutes in full sunshine! The torments of the unfortunate patient undergoing this ordeal are very graphically described. The name of Fox Talbot, who had succeeded in fixing the photographic image on paper

642

FIG. 1.-Facsimile of a microscopic despatch used during the siege of Paris. and then in a position which we cannot but consider as too subordinate, to which effect the editor has added a note.

The next stage of photographic history brings us to the time of Niepce de Saint-Victor (nephew of the Niepce who was in partnership with Daguerre), who first discovered the albumen on glass process. The application of collodion to photography by Legray in France, and Scott Archer in England, brings the art down to its present state of development, and the author at this stage brings the historical portion of the subject to a conclusion. In the second part of the work the operations and processes of photography are dealt with in seven chapters. The watchful vigilance which the editor has kept over the interests of British science has here for once failed. The whole credit of the bichromate of potash and gelatine process the foundation of all the photographic permanent printing processes-is more than once in the course of the work assigned to Poitevin. "The various processes

or producing positive carbon prints," writes M. Tissandier on p. 162, "are based on the principle indicated by Alphonse Poitevin in 1855." We must remind our readers that a patent for the use of bichromate and gelatine in steel engraving was taken out in this country by Fox Talbot in 1852.

Of the carbon processes that of Swan is described by the author, and the editor adds a brief account of the most recent improvements in this branch of the art adopted by the Autotype company. The last chapter of this part relates to the problems yet awaiting solution, and is chiefly devoted to an account of the attempts which have been made to photograph in natural colours.

The third and last part of M. Tissandier's book treats of the applications of photography. In the first chapter we have a description of the various heliographic and

photo-lithographic processes which have from time to time been invented, including those of Donné, Fizeau, Niepce de Saint-Victor, Poitevin, Baldus, Garnier and Salmon, Albert, and Obernetter. The second chapter, under the title of "Photoglypty," is devoted to a description of the Woodbury process, after which follow two chapters on photo-sculpture and photo-graphic enamels. Chapter V. treats of photo-micrography, and is illustrated by several excellent engravings of photographs of microscopic objects. The following chapter describes the application of photography to war. The method of sending microscopic despatches by carrierpigeons adopted during the siege of Paris will be of interest to our readers. The despatch having been printed was reduced by photography on to a collodion film, which was then rolled up and enclosed in a quill, which was fastened to the tail of the pigeon. We here reproduce a facsimile of one of these microscopic despatches. To read the despatches sent in this way the collodion film was unrolled by immersion in weak ammonia water, dried, placed between two glass plates and a magnified image projected on to a screen by means of a photoelectric microscope (see Fig. 2).

Chapter VII. treats of astronomical photography, and touches upon the results achieved in this branch of the art by Warren De la Rue, Secchi, Rutherfurd, Grubb, &c. The author is not quite accurate when he states that for astronomical photography "it is indispensable to make use of a reflecting telescope having a speculum formed of glass silvered according to Foucault's process." The experiments of Rutherfurd show that lenses may used with excellent results. Chapter VIII. describes photographic registering apparatus, barometric, thermometric, magnetic, electric, &c.; and Chapter IX. is devoted to stereoscopic photography.

be

Chapter X. treats of the applications of photography to art, while the last chapter discusses the future of pho

tography. The author expresses a hope that among other developments which the art is destined to undergo, the time may come when it will be possible to photograph by telegraphic means.

The foregoing sketch of the book will be sufficient to enable our readers to form an estimate of its contents. The translation appears to have been carefully made, and the engravings, of which there are over seventy, are excellent. The frontispiece portrait, by B. J. Edwards and Co.'s photo-tint process, is a beautiful example of permanent photographic printing. In conclusion, we can heartily commend M. Tissandier's book as a popular exposé of photography.

OUR BOOK SHELF

R. MELDOLA

Morocco and the Moors: being an Account of Travels, with a General Description of the Country and its People. By Arthur Leared, M.D. Oxon, F.R.C.P., &c. (London: Sampson Low and Co., 1876.)

MANY readers, we believe, know less about Morocco than they do about Lake Tanganyika, the Fiji Islands, or the Arctic regions. Not that there are no easily accessible works on the country; no one, we conceive, who might be anxious to get up" Morocco would have much difficulty in collecting trustworthy authorities,

66

both in English and French. The modern general reader, however, has so much to do to keep up with a decent percentage of the literature of the day, that, unless for a travel of a past generation; therefore, even for countries special purpose, he is not likely to unshelve works of near at hand and whose names occur almost daily in Reuter's despatches, it is useful now and again to have the narrative of a recent visit. Morocco, though comparatively near us, yet in many respects is so isolated and condition is welcome.' Dr. Leared was only a few weeks so far behind the age, that a trustworthy account of its in this country in the autumn of 1872. He landed at Tangier, visited the neighbourhood, sailed down the coast to Mogador, calling at one or two places on the way, and at a time of great internal disturbance visited the city of Morocco, where an attempt was made to poison him, hapHe managed to make a very good Pily without success. use of his time and his eyes and his introductions, and the reader will find many interesting observations on the people and the country. Dr. Leared has, however, not confined himself to his own observations, but has evidently diligently studied various authorities on the country, and taken trouble to acquire information from work as he goes along, and especially in a series of convarious quarters. The results he presents throughout the cluding chapters on the country and the people, government, law, education, superstitions, agriculture, natural history, &c. The appendix contains a variety of valuable material, including meteorological observations for Tanwith the value of Morocco as a resort for phthisical gier and Mogador. Dr. Leared is strongly impressed patients, the climate in some parts, he thinks, being in this respect superior to that of almost any other place. To anyone wishing to have a pretty full, and on the whole trustworthy account of the present condition of Morocco, we can honestly commend Dr. Leared's book, which, we should say, contains a small map and numerous illustrations.

Tyrol and the Tyrolese: the People and the Land in their Social, Sporting, and Mountaineering Aspects. By W. A. Baillie Grohman. With numerous illustrations. WHATEVER other qualities Mr. Grohman's book may (London: Longmans, 1876.) is by birth half a Tyrolese, and he has spent several possess, it is at least intensely interesting. The author years in the country, evidently living frequently in all respects as a native, and thus having unusual opportunities of becoming thoroughly acquainted with the country and the people. What we have said in speaking of Dr. Leared's work on Morocco, might be applied with equal force to Tyrol, which, although the yearly resort of hundreds of tourists, is known to most only on the sur face. Mr. Grohman's chapters give one a very satisfactory idea of the character and customs and general life of the people, and his sketches of the mountain scenery and of the habits of the chamois and black-cock are interesting, and in the latter case may furnish naturalists with a few additional facts. The people themselves are evidently made of splendid stuff, but at present rough and raw, and sorely in need of being polished. They are overridden with superstition, and in many of their customs, especially in the matter of social morality, have a strong resemblance to what the Scotch were generally a generation or two ago, and are still in some remote districts. The book is mostly occupied with Mr. Grohman's personal adventures, and one is sometimes inclined to suspect that these have been pieced together so as to tell effectively. however, simply adds to the interest, and does not detract from the value of the work. One of the most interesting chapters describes an ascent of the Gross Glockner in the dead of winter by the author and four guides. The illustrations are very beautiful, and the book, we should think, is likely to find many readers,

This,

LETTERS TO THE EDITOR

[The Editor does not hold himself responsible for opinions expressed by his correspondents. Neither can he undertake to return, or to correspond with the writers of, rejected manuscripts. No notice is taken of anonymous communications.]

The Late Eclipse

AN answer to Mr. Proctor (vol. xiii. p. 186) is unnecessary to those who know all that has been written on the possibility of photographing the spectrum of the corona, but I take the liberty to give a few quotations out of the literature on the subject for the benefit of those who take an interest in the discussion, yet had no opportunity of following it in detail. Want of space

prevents me from quoting all the letters in full, but I believe that I have not left out anything which might alter the sense of the quotations. The passages which seem to me to be important to the point at issue are printed in italics.

I. Letter to the Editor of the Daily News, signed Richard A. Proctor, January 26, 1875 :

"It is said that some enthusiastic students of science propose to try to get photographs, not of the corona as seen in a telescope, but of the exceedingly faint coronal image seen with a spectroscope. If they succeed they will have achieved a clever photographic feat, but the result, so far as the corona is concerned, can have little scientific value. It is mathematically demonstrable that this is the case, for the quantity of light actually forming the coronal image can be shown to be far less in amount than is necessary for the formation of a satisfactory photograph." 2. Letter signed A Fellow of the Royal Astronomical Society" (English Mechanic, May 21, p. 248):

66

"But if Mr. Proctor should take upon him to answer the first of these questions in the affirmative, the second in the negative, then I could ask him whether any body or any set of men possessing the slightest knowledge of the subject could or would have issued the preposterous instructions about photographing the spectra of bright lines in the corona, which emanated from the Royal Society? The bright lines in the corona ! Why, it has been recorded again and again by skilful observers that so faint is the light of the whole corona during the totality of a solar eclipse, that it casts no shadow whatever; and we know that the outer parts of the corona failed utterly to impress a collodion plate in five seconds, upon which a sharp and effective image of the partially eclipsed moon impressed itself in o'r second with a longer focussed telescope!

(I should not have quoted in your columns any remarks of this anonymous writer had not Mr. Proctor's reference to them in the following letter rendered it necessary.)

3. Letter from Mr. Richard A. Proctor (English Mechanic, May 28, 1875, p. 272) ::

"With respect to the eclipse observations last April, I have already said, as 'F.R. A.S.' does (let. 9,113, p. 248), that the failure of the Government expedition was rendered certain by the instructions of the Royal Socie'y Committee. I pointed this out also before the expedition started. I agree with F.R.A.S.' entirely in his interpretation of the matter."

·

Taking these letters in connection with what Mr. Proctor now writes, the following seems to be Mr. Proctor's opinion :

It is mathematically demonstrable that "the quantity of light forming the coronal image is far less in amount than is necessary for the formation of a satisfactory photograph" (Daily News), yet "Dr. Schuster proves very readily that the spectrum of the corona can be photographed in one minute" (NATURE). Mr. Proctor "is not aware that anyone has questioned the fact," but he "fully agrees with an anonymous writer that no set of men having the slightest knowledge of the subject could have issued the instructions which emanated from the Royal Society.'

The failure of the Eclipse Expedition was rendered certain by the instructions of the Royal Society Committee to photograph in four minutes what Mr. Proctor admits to be capable of being photographed in one minute.

Anything which Mr. Proctor could have written on the subject besides what has been quoted, as, for instance, the passage in "Science Byeways," he alludes to in his letter, can only add to the hopeless confusion which must bewilder anyone trying to form a correct and fair estimate of his view on the matter. Everybody will agree with Mr. Proctor that such a contro versy is not likely to be of any service to science.

The Fossil Skeletons of Le Puy en Velay France in Auvergne and Velay next summer, it may be useful As there is to be a meeting of the Scientific Congress of difficulties connected with the supposed antiquity of the fossil to direct attention, through the columns of NATURE, to certain human bones preserved in the Museum of Le Puy.

With respect to the position of the bones, I visited the locality they were supposed to be found in last September, in company with some friends, and we were conducted, by the peasant who professes to have found them, to a well near the little auberge, where he now resides, and which is certainly a very different spot to that indicated by Mr. Poulett Scrope in his sketch at page 182 of the "Volcanos of Central France." The locality given by Mr. Scrope is much higher up the hill than is the well we were shown near the "Hermitage." Sir Charles Lyell also, according to the "Antiquity of Man," p. 229, was conducted to a spot "not far from the summit of the volcano." The well of the Hermitage is a long way from the summit of the hill.

It has long been observed that the rocky matrix in which the human bones have been enveloped is altogether different from the matrix of the rock where they are said to be found. This is certainly the case as regards the matrix of the rock in which the well is situated, which is a coarse volcanic breccia, while the bones lie in a volcanic sandy mass with a mixture of tuff and lime. I especially wish to direct attention to the position of one of the larger bones marked (I think) as an "iliac bone" in the Museum. The laminated mass between which it rests appears to me stalagmitic, as if these human remains had been washed into a fissure through which the water percolates downwards to the well of the Hermitage, and of which traces may be found higher up the hill.

I would also direct attention to certain stratified breccias near the western summit of the hill of Denise, which we thought looked more like the result of melting snow and the action of running water than of "volcanic alluviums," to which they have been generally attributed. These may be seen beyond the Croix de Paille on the road to Briowde high up on the flanks of the hill west of the volcanic outburst known as "The Chimney." The black and red scoria shot out through this "chimney" cover the summit of the hill and overlie the stratified breccias. But these breccias are, if I read the geology of the district aright, the equivalents of those which, on the slopes of Denise, west of Polignac, have furnished the bones of the mammoth and tichorhine rhinoceros, and belong to glacial times.

The antiquity of the human skeletons must, I suggest, depend upon the correct determination of the spot where the bones were found. It is possible that they may belong to the age of the stratified breccias, and were washed into a crack or fissure during the Mammoth epoch, but they certainly do not look like it, if we may judge from the matrix in which they are enclosed. It is possible that they were enveloped in volcanic materials which were evolved during the last volcanic outbursts, for I believe that at Le Puy en Velay and in the Ardèches there have been eruptions of scoria and ashes through volcanic vents and chimneys since the glacial epoch, when deep snows covered the summit of Denise in the winter time and the mammoth pastured in the vales. W. S. SYMONDS

A Meteor in the Daytime

THE meteor referred to by the Rev. T. W. Webb was also seen at Dorking and at Southampton. The times given were "about 1.38 P.M." and "1h. 38m. 45s. P. M.," Dec. 22. Mr. H. J. Powell, writing to me from the former town, says: "Its course

was from S.S. E. to N.N. W., and it shot down the sky soIt had no well-defined outline like the moon, but was merely an irregular luminous ball. Its size as compared with the moon was about one-sixth. Its motion was not a very rapid one, but more like a cricket ball (after it has been thrown) falling. I did not hear any sound after its disappearance." Mr. Powell, writing to the Times, also mentioned that it "left a long trail of before it had reached the horizon." fire behind it," and that the nucleus "broke up and disappeared

In the Times of the same date (Dec. 23), "F. W. " writes: "In the full blaze of the sun-a rare sight in itself nowadays-I observed a bright meteor traversing the sky from south-west to north-east, in form like a common rocket."