Weigert's method of preparing and staining nerve-tissue is given, but with one important detail left out, viz., that on removing the specimen from Müller's fluid or chromic acid solution it should have a brown, and not a green colour. The preparation of individual tissues and organs is well dealt with in chapter xii., but in the succeeding one on the examination of tumours there are such evident signs of hasty composition as to render it of small intrinsic value. On the other hand, the important subjects of urinary and excrementitious matters receive ample treatment; and we have a clear résumé up to this date of all that is taught on these subjects. As an example we note with pleasure the account of Dr. Delepine's work on 66 "sable intestinal." The bacillus of Asiatic cholera and the methods of its detection are described on p. 228; and the diagnostic points between it and that of cholera nostras are found on the next page. A large amount of space is necessarily devoted to the examination of sputa. Dr. Wethered's experience at the City of London Hospital for Diseases of the Chest enables him to speak with the voice of authority on the signification of the presence or absence of the tubercle bacillus. Physiologists will find their side of the question well considered in the observations on blood; on Dr. A. Garrod's authority we are told that the blood of the Londoner has not yet been found to contain its true proportion of hæmoglobin. Eosinophile cells are not omitted; but for more detailed information on this point we commend to the notice of pathologists the article by Dr. A. Kanthack in the British Medical Journal of June, 1892.

Medical microscopy as a subject is exceedingly elastic, and we believe Dr. Wethered has stretched it to its widest limits when he finds space for describing the examination of various kinds of cereals, also of water. Even the homely tea-leaf has not escaped his notice. A few instances of clerical errors are to be found, thus Hartnach for Hartnack, on p. 122, Richert for Reichert. At the term "collodionization " we venture to express our distaste. A growing practice exists of introducing ungainly expressions of doubtful expediency into scientific works.

We have read this book with considerable attention, and are convinced that it has a most distinct raison d'être, and justifies on the whole, by the merit of its execution, the ambition of its title. It treats of the matter in hand with much ability, and in a manner that evidences considerable experience on the part of the author as a pathologist, physician, and teacher.

ODOROGRAPHIA.

A. H. TUBBY.

is probably due to the fact that but few persons possess the requisite knowledge to treat the subject in a thoroughly satisfactory manner in all its bearings, such as the origin and production of the numerous products, whether animal or vegetable, and the chemical aspect of every substance and its commercial value, which are points that could scarcely be expected to be mastered by one mind. In the "Pharmacographia" of Flückiger and Hanbury, two master minds on the subject of drugs were brought into co-operation, with the result that a most satisfactory and standard work on medicinal plants was produced. That this book was in the mind of the author when he compiled his "Odorographia," and selected its title, is quite apparent, and we are bound to say that on the whole he has done his work remarkably well, though we wish that he had adhered more strictly to the lines of his pattern. Mr. Sawer, however, at the very commencement of his preface, is so modest as to say that "an endeavour has here been made to collect together into one manual the information which has hitherto been only obtainable by reference to an immense number of works and journals, English and foreign, in many cases inaccessible to readers interested in the subject,” and that he is thoroughly well acquainted with all that has been written is apparent not only from a glance through the pages, where numerous references occur, but also from the "List of Principal Works referred to." Besides this the author has, as he tells us, obtained information first hand from some of the largest perfume-plant growers and manufacturers of Grasse, Nice, and localities in the Straits Settlements and West Indies. The difficulties attending the compilation of a work of this nature have, no doubt, been very great, because scraps of information are so widely dispersed, and even when found oftentimes very confusing. The botany alone of the subject must have occupied a considerable amount of time in looking up, the plants yielding perfumes being natives of various parts of the globe, and consequently described in the several floras appertaining to those special countries, besides which the chemical and commercial aspects occupy a large portion of the book.

Though we are grateful to Mr. Sawer for giving us a book that was really wanted, we regret, as we said before, that he has not followed more closely the plan of the "Pharmacographia" and arranged his matter under distinct heads, such as History, Botany, Cultivation. Chemistry, Commerce, &c. Practically he has done so to a certain extent, but the paragraphs are not sufficiently distinguished to enable one to turn at once to that upon which information may be specially sought. The arrangement of chapters, in which the most important and marked odours, such as those of musk, rose, violet, the citrine odours, &c., are brought together, is good, but the principal plants in each of these groups might have been treated as we have described, the least important ones being given as they are at the end of the chapters.

Returning to the botany of the book, we cannot but think that the author might well have spared much space by the omission of numerous varietal names and synonyms, many of which are scarcely ever heard of now, and which often only tend to confusion. Under Violet, for instance (p. 104), half a page is given to a list

of the names of nine varieties of the Sweet Violet (Viola odorata). Again, at p. 309, Vétiver, or Cus Cus, is rightly described as the root of Andropogon muricatus, after which follow the names of five synonyms. In reference to this Mr. Sawer says, referring to the "Asiatic Researches," that "there is a verse in the Sanskrit language composed of nine words, arranged in two lines, purporting to be the nine names under which the plant was known; doubtless they were poetical names, as they are not found in the extensive list of local names recently enumerated by Watt." This would show that Dr. Watt, who in his "Dictionary of the Economic Products of India" does not err on the score of brevity in the adoption of synonyms, considered that there was a line to be drawn somewhere. We may perhaps also be allowed to draw attention to a paragraph on page 19, where the musk tree of Jamaica and the muskwood of Australia have got confused. The paragraph in question runs thus: "The Eurybia argophylla or Guarea Swartzei, the silver-leaved musk tree of Jamaica, New South Wales, and Tasmania, is a meliaceous tree, attaining a height of twenty-five feet." Eurybia, or more properly Olearia argophylla is the muskwood of New South Wales and Tasmania, and belongs to the natural order Compositæ, while Guarea Swartzii is a meliaceous tree of Jamaica, where it is known as musk tree. Another muskwood, not mentioned by Mr. Sawer, is that of Moschoxylum Swartzii, a highly fragrant resinous tree, closely allied to Guarea, and a native also of Jamaica and Trinidad. We refer to these matters in no captious spirit, but simply with the hope that Mr. Sawer may see his way to overhaul and modify this part of his useful book in a future edition, so as to make it even more useful and trustworthy. We are glad to note that he "is still engaged upon studies in this department, and hopes to publish another volume in due course."

are expressly stated to be in" Coll. Saunders," all the others are in the British Museum, including those for which a locality is given before the list of British Museum specimens.

Charles Darwin: His Life Told in an Autobiographical Chapter and in a Selected Series of his published Letters. Edited by his son, Francis Darwin. (London : John Murray, 1892.)

PROF. DARWIN describes this volume as practically an abbreviation of the well-known "Life and Letters." The task of compression has been accomplished admirably, and there can be little doubt that the work will be cordially appreciated by a large number of readers. Of course it has been necessary to omit many details which are of interest to men of science; but everything is included which is really essential to a proper comprehension of Darwin's fine personal character, and a sufficiently full and clear idea is given even of his scientific labours. No one will read this fascinating book without feeling anew how much reason England has to rank Darwin among the greatest and noblest of her sons. The volume is enriched with a reproduction of an exquisite photograph of Darwin by the late Mrs. Cameron.

Strange Survivals: Some Chapters in the History of Man. By S. Baring-Gould. (London: Methuen and Co., 1892.)

EVERY one who has given any attention to anthropology is aware that many remarkable customs and beliefs, which are still to be found among the uneducated classes even in highly civilized communities, are relics of ancient superstitions. In the present volume Mr. Baring-Gould examines various groups of these curious survivals, and traces them back to their origin in the ideas of past ages. He knows his subject well, and, being interested in it himself, is able to present it in a way which is likely to make it interesting to others. The value of the text is considerably increased by some well-selected illustrations.

OUR BOOK SHELF.

Catalogue of Eastern and Australian Lepidoptera Heterocera in the Collection of the Oxford University Museum. By Colonel C. Swinhoe. Part I. Sphinges and Bombyces. (Clarendon Press, 1892.)

THIS volume is the first part of a Catalogue of the moths from the Oriental and Australian regions in the collection of the late Mr. W. W. Saunders, which was acquired by the Oxford Museum some fifteen years ago, and consists chiefly of specimens collected by Wallace during his famous voyage to the Malay Archipelago, and described by the late Francis Walker in his British Museum Catalogue. Since Walker's arrangement of the collection it has remained untouched and mostly neglected by lepidopterists, so that a rearrangement and comparison of the types had become highly necessary, which useful work has been undertaken and very ably carried out by Colonel Swinhoe. All the types have been brought to the British Museum, their synonomy carefully worked out and the species placed in their proper families and genera, many of them being fi ured in the eight coloured plates, and it is to be hoped the other parts will soon follow, and also that a list of the types which should be in the Museum and are missing will be added. There is one statement in the preface which requires correction; the only types of Walker's species described in his Catalogue which are in the Oxford Museum are those which

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 intended for this or any other part of NATURE.. No notice is taken of anonymous communications.]

Botanical Nomenclature.

IN NATURE for October 6 (p. 549) there is a note "on the progress of the negotiations concerning the nomenclature of genera, started by a committee of botanists at Berlin to supplement the decisions of the International Botanical Congress held at Paris in 1867." It is stated that "the botanical authorities of the British Museum favour the suggestions; those at Kew are against them."

Now this requires a little correction. It may be remarked to begin with that many botanists are exercised at the present time not merely about the nomenclature of genera, but also about that of species. Kew has, however, never given its adhesion to the attempts that have been made to bring about an international agreement on these matters. It has always felt that so many considerations must determine the course taken by the systema ist in any particular case, that there is no advantage, but positive inconvenience, in being subjected to a hard and fast rule. It is therefore with no disrespect to, or want of sympathy with, the able school of Berlin botanists, who have recently formulated some new proposals with regard to n menclature, that Kew has officially refrained from expressing any opinion upon those proposals. It has neither expressed approval nor disapproval.

In America Harvard has long occupied the leading place in the botanical world, and the principles adopted there have been substantially in accord with those adopted at Kew. Hitherto,

therefore, the leading English-speaking botanists who have occupied themselves with systematic botany have been in substantial agreement that the adoption of a strict law of priority in nomenclature must give way to considerations of convenience.

Well known and accepted names are not therefore to be lightly changed as the result of mere bibliographical research. As to specific names the often merely mechanical process of describing a new species is held to be of little value compared with the more difficult task of assigning to the plant described its true affinities and correct systematic position. The principle which guides Kew practice in this matter is laid down by Sir Joseph Hooker in the preface to "The Flora of British India" (p. vii).

He remarks:

"The number of species described by authors who cannot determine their affinities increases annually, and I regard the naturalist who puts a described plant into its proper position in regard to its allies as rendering a greater service to science than its describer when he either puts it into a wrong place or throws it into any of those chaotic heaps miscalled genera with which systematic works still abound."

The following paper on the subject deserves the wider circulation which its reprint in NATURE would give it. It represents the Harvard tradition and practice, and is the last scientific utterance of Dr. Sereno Watson, who so soon followed to the grave his illustrious predecessor, Asa Gray. Kew, November 14. W. T. THISELTON DYER.

ON NOMENCLATURE.1

[It was the request of the late Dr. Sereno Watson that the following com. munication, dictated by him in his last illness, should appear at an early date in the Botanical Gazette.-EDS.]

FOR Some time I have had a desire to give expression to my views upon botanical nomenclature. Under the circumstances, I must speak briefly and somewhat dogmatically. In my opinion botany is the science of plants and not the science of names. Nomenclature is only one of those tools which is necessary to botany, and this being the case, points of nomenclature should be subordinated to science.

A principle of botanical convenience has been established by those who prefer one name to another on account of expediency or convenience. This principle should have a great deal of influence. It has been so recognized by the greatest botanists, and from their authority receives great weight. I prefer the word expediency as a better term than convenience to designate the principle, that the demands of science over-ride any merely technical claims of priority, &c.

Priority of specific names appears to be based entirely upon one section of the code of 1867. That simply says that when a species is transferred from one genus to another, the specific name is maintained. This principle is usually understood and applied in the way that the oldest specific name has a right in all cases to be retained. It cannot fairly be so interpreted and applied, since it governs only to the extent that this should be the law, but it is not to be made an ex post facto law. Thus when a transfer has been made, that ends the matter so far as the choice of a specific name is concerned, and no one is authorized to take up a different name. This practice of retaining the oldest name under the genus, no matter what older specific names there may be, was adopted by Dr. Gray in his later years and by the Kew bot

anists, for the reason that once established and pretty generally recognized, it would avoid the great mass of synonymy, which is being heaped like an incubus upon the science. I must express surprise that Dr. Britton had not considered it his duty to publish the last written words of Dr. Gray which were addressed to him upon this subject and which expressed his positive opinions upon this point.

There is nothing whatever of an ethical character inherent in a name through any priority of publication or position which should render it morally obligatory upon any one to accept one name rather than another; otherwise it would be applicable or true as well in the case of ordinal names, morphological names, teratological, and every other form of name, to which now no one feels himself bound to apply the law of priority. The application of this law as at present practised by many botanists, which would make it the one great law of botanical nomenclature, before which every other 1 From Botanical Gazette, vol. xvii.

must yield regardless even of common sense, is a mere form of fetichism exemplified in science. Many instances of the application of this law are not science but are rather superst tion. SERENO WATSON.

February 22, 1892.

The Reflector with the Projection Microscope. THE lantern is now used for so many purposes-scientific photographic, and recreative-that any improvement in its construction will be acceptable. When we look into this instrument whilst at work we must be disappointed at the large quantity of light lost by reflection and by dispersion-light which ought to go to the illumination of the screen. In the ordinary form of the lantern three lenses of dense glass are employed as condensers. Each of these six surfaces reflects and scatters the light, and the glass itself is absorbent of is

rays.

The dioptric construction of the projection lantern has bet well worked out by Messrs. Wright, Newton, Salomons, and others, but the catoptric principle, which would eliminate almost entirely these disadvantages, has been scarcely at al studied.

Although my experiments have been made solely with the limelight in various forms, the following remarks may equally apply to light given by the electric arc :

If a reflector be used instead of the ordinary condensers i is obvious that the position of the lime cylinder must be reversed. This will present no difficulty, for the tube holding the jet car be bent into a helical form. The dark image of the limecylinder also will have no more practical disadvantage than is experienced by a like image formed by the small plane specalum of the Newtonian telescope.

As to the mirror itself, although a parabolic form is the most correct, a spherical surface will be sufficient for mere illumiaating purposes, and thus expense may be spared in the grind ing of the more difficult curve. A speculum of from 5 to 7 inches diameter, having a radial curvation of from 2 to 3 inches, will grasp a large quantity of light, much more than that obtainable from the 5-inch condenser usually employed.

Silver deposited by one of the various reducing processes on the surface of a clear glass lens will have many advantages over a metal mirror. The front surface will give perhaps the finest definition, but by silvering the back part of a spherical glass film, or that of a ground lens, the brilliant surface will remain untarnished for an indefinite time, and the whitish bloom formed by slow volatilization of the incandescent lime is easily removed. This silver film adheres with remarkable tenacity, and it will bear a great deal of heat without blistering a becoming detached.

I have had considerable success in constructing such mirrors from the large ornamental glass spheres blown in Germany, and silvered within by Liebig's process, viz. with milk sugar and ammonio nitrate of silver. A glass sphere of 10 or II inches in diameter may be easily cut into eight or nine mirrors by a red-hot iron, and this without disturbing the silvering, which will require only gentle friction with a pad of cotton impreg nated with a trifle of rouge to brighten it. Thus, at the cost of a few shillings, eight or more mirrors can be made, and also provision be made against possible accidents of cracking by heat.

cepted by a plano-concave lens of dense glass, as has been hap

The light-radiant is so placed that the secondary focus is inter

pily proposed by Mr. L. Wright. The convergent rays from the speculum are thus made into a parallel beam, which must be de prived of its heat by an alum-trough, for the light and heat at the substage condenser is very great.

Convergence, I find, is usefully promoted by a plano-consex lens of about eight inches focus, placed two or three inches before the above-noted plano-concave lens. In all other respects the arrangements are like those of the usual modern projection microscope.

I have pretty constantly used the ether-oxygen saturator, and I consider it to be perfectly safe, if ordinary precautions be taken. The oxygen, compressed in cylinders, is much recommended, as there can be no mixture of vapour, except at the right place. The U-shaped horizontal saturator, plugged with flannel, must be well charged with ether, or with the best gaso lene, and care should be taken, before beginning or ending 2 exhibition, to shut off the oxygen tap before closing the ether