metrical law of generation was described and the position and aspect of its principal elements indicated on the paper. Its indication was then complete, and the representation of any points or lines upon it was then reduced to the devices of practical geometry. The principle simply was that a surface might be regarded as completely known when we had indicated a method of taking an infinite number of sections of it. In the simplest case, these would be parallel plane sections, as in the ordinary drawings of a ship, but Monge's method was not trammelled by this restriction.

Like most large subjects, it is one which it is very difficult to know how to treat with advantage to the, student. An exhaustive treatise is out of the question for any learner who is not prepared to make it an exclusive or principal study, and it is a matter of very nice judgment what to select and how much to present to the pupil; and this is the more emphatically so, inasmuch as it is really the only good introduction to a practical insight into the geometrical properties of space.

Viewed in this light, the treatise before us is an exceedingly good one. With great clearness and precision, it covers a considerable extent of ground, and that by no means baldly; and yet it is not too long. It has, moreover, a very valuable adjunct, and one which, we believe, is quite new-a series of stereoscopic drawings exhibiting the actual construction in solido of thirty-six of the principal problems. To the ordinary student this will be of immense assistance; for it is well known to teachers of geometry and of mechanics, that want of imagination on the part of the student is one of the principal obstacles they have to deal with in endeavouring to impart to him accurate conceptions of space and of motion. These drawings have been very clearly and judiciously executed by Prof. Saint Loup (of Paris), and slight colouring has been introduced in some of the examples of intersection with marked advantage and success.

We notice some peculiarities of language in which English usage is slightly departed from, as in writing warped surfaces instead of skew surfaces, in spelling the word directer with two e's instead of "director," and in the use of the word raccord to express that two surfaces have a line of contact. Some of these, having regard to the unsettled English nomenclature of an imported subject, are not blemishes, and none of them detract from the really high value of the book.

Some account is also given of the leading spherical projections, especially the orthographic and the stereographic. These are important additions to the treatise, and although we would gladly have seen some others described, particularly the gnomonic projection, we think the author has done wisely in not unduly extending this part of his treatise.

The book is of convenient size, clearly printed, and well arranged, with a good table of contents. Altogether, we think it one of the best books upon the subject which we have yet seen, especially in English, and we think it does the highest credit to the distinguished American professor who is its author.

It is certain that Monge did a great deal to systematise and complete the method; but some of its principles were certainly known, although carefully kept secret, in some of the higher French schools. In consequence of this secrecy, it will probably never be known exactly how much is due to Monge; but we may well believe that Monge did for this science what Newton and Leibnitz did for the infinitesimal calculus.

PHILLIPS' "ELEMENTS OF METALLURGY" Elements of Metallurgy: a Practical Treatise on the Art of Extracting Metals from their Ores. By J. Arthur Phillips, M. Inst. C.E., F.G.S., F.C.S., &c. (London: Charles Griffin and Co., 1874.)

OF

F all the sciences, Metallurgy is the one whose history extends into the most remote antiquity, and there is abundant evidence to show that even complicated metallurgical operations were performed empirically long before the physical sciences existed.

Until within comparatively recent times the number of eminent chemists who devoted themselves to metallurgical work was more commensurate with the importance of the subject than at the present day, when, we venture to think, too many are lured away by the attractions of organic chemistry and abstract speculations as to the existence of matter. Notwithstanding this, within the last few years the science of metallurgy has made great advances, but the works on the subject published in this country have been singularly few; Dr. Percy's admirable work is still incomplete, and, with the exception of the translation of Kerl's "Metallurgy" by Crookes and Röhrig, there is no work which is even fairly comprehensive. The edition of Mr. Phillips' "Manual of Metallurgy" published in 1858 has become almost useless, but the volume just issued is an important addition to this branch of literature.

The physical properties of metals are fully and carefully treated, and eighty pages are devoted to the consideration of fuel. The description of iron ores is very good, the author having closely followed Bauerman, and no pains have been spared to render the portion of the work which treats of iron as complete as possible. Among the numerous carefully executed engravings are drawings of roasting and calcining kilns, and of the blowing engine and blast cylinder at Dowlais.

The next important metal, copper, is discussed at some length, and the description of the "wet methods" of extracting this metal is specially valuable, as the author writes from long experience of operations which have been conducted under his own direction. It is interesting to note that processes such as those carried on at Widnes, Alderley Edge, and Jarrow-on-Tyne, are applications, on a manufacturing scale, of methods ordinarily used by the chemist in his laboratory, and, as such, they afford singu larly important evidence of the progress of metallurgical

science.

Lead is treated at some length, special attention being devoted to the extraction of this metal by means of reverberatory furnaces. Excellent drawings are given of those employed in the works at Couëron, where galena associated with carbonate of lead is partially converted into oxide and sulphate by roasting, which subsequently react, at a more elevated temperature, on the undecomposed sulphide in the charge, producing metallic lead.

The articles on silver and gold are condensed from the author's well-known work on the mining and metallurgy of these metals, some new matter being added; they leave little to be desired, but the forms of apparatus for assaying which are described, are not in all cases the most perfect.

Fifteen metals are treated in the work, and these are

by far the most important commercially; nevertheless, we could have wished to find brief accounts of such metals as manganese, magnesium, cadmium, palladium, potassium, and sodium.

We have already referred to the excellence of certain drawings, and it is only necessary to add that throughout the volume the illustrations are of very high merit. They are evidently drawn from actual measurement, but it is to be regretted that scales are not given.

The author states in his preface that the object which he had in view was "to supply, within moderate limits, such practical information on general principles, and typical processes, as may not only afford a comprehensive view of the subject, but also enable the reader to study with advantage more elaborate treatises and original memoirs." Certainly this object has been attained; and we think he has done more, in that he has produced a work which not only fully sustains his reputation, but affords fresh evidence of his having done much scientific work of a kind far too rare in this country.

OUR BOOK SHELF

Descendenzlehre und Darwinismus. Von Oscar Schmidt. (Leipzig Brockhaus, 1873.)

THIS volume of three hundred pages is one of the "International Scientific Library." It is a moderate exposition of the Darwinian theory of Evolution, intended for general readers, and while free from the eccentricities of Hæckel's Anthropogenie, also lacks the brilliancy and power which redeem its faults. Prof. Schmidt while still at Gratz became a convert to "the new philosophy," and in his Vergleichende Anatomie (NATURE, vol. v. p. 228) adopted its conclusions as the basis of his teaching. In a paper read before the "British Association" of Germany two years ago, at Wiesbaden, he stated and defended his change of opinion, and now that he is established as professor in Strassburg University, he puts forward this volume as a fuller exposition of his views-" for here one must show one's colours." It is perhaps undesirable for people to attempt arriving at the results of science by such easy roads as popular treatises, and "The Descent of Man" itself is a better interpretation of Darwinism than the expository treatises of Darwinists; but there is undoubtedly a demand for books of this kind, and if they are to be written, it is well that so competent a hand as Prof. Oscar Schmidt's should do it. There are several woodcuts, a good list of references, and the inevitable genealogical trees.

We also note the appearance of an essay attacking the theory of Evolution, by Prof. Wigand, of Marburg; and a reply to it by Prof. Jäger, of Stuttgart. The former, entitled Darwinismus und die Naturforschung Newton's und Cuvier's, is a temperate production, written from the point of view of a botanist. The latter is a more lively rejoinder, and appears as In Sachen Darwin's_insbesondere contra Wigand.

P. S.

The Micrographic Dictionary: a Guide to the Examination and Investigation of the Structure and Nature of Microscopic Objects. By J. W. Griffith, M.D., and A. Henfrey. Third Edition, edited by J. W. Griffith and Prof. M. Duncan, assisted by the Rev. M. J. Berkeley and T. Rupert Jones. (London: J. Van Voorst, 1875.)

WE have from time to time chronicled the progress of this work, and have now the satisfaction of announcing its completion. In a work of this kind, which has been upwards of three years in passing through the press, it is inevitable that minute criticism should detect some

discrepancies between the various articles, and some passages in the earlier pages which would not have been written in the light of more recent investigations. It is probable, also, that workers in different fields will place a different estimate on the importance of their own department, and will be disposed to grudge the space devoted to others. The student of Cryptogamic Botany has at all events the lion's share, almost every genus in some groups being described. In the present chaotic state of the classification of Cellular Cryptogams, it is probable that a number of the genera and even groups treated of in this work as autonomic will have ultimately to be abandoned. There is, however, so much that is of the greatest value to every microscopist, that we can cordially recommend the work as indispensable to the student. The plates, some of which are new, and others re-drawn, are of themselves of great and permanent value.

Temperature Chart of the United States, showing the Distribution by Isothermal Lines of the Mean Temperature of the Year. Constructed under the direction of Prof. J. Henry, Secretary, Smithsonian Institution, by Charles A. Schott, Assistant U.S. Coast Survey, in October 1872.

THIS temperature chart, which by the way should have been accompanied with some explanatory remarks, has been issued by the Smithsonian Institution. The isothermals are given for every 4° F., beginning with 36° in Minnesota and the northern shores of Lake Superior, and rising successively to 76° in the extreme south of Florida. The lines have evidently been drawn from mean annual temperatures, uncorrected for height, and are therefore designed to show the actual distribution of mean annual temperature over the surface of the United States. This method of representing the distribution of temperature, which has been employed by Petermann and others, is well suited for various purposes for countries, such as Russia, which consist chiefly of extensive rolling plains; but it is not suited for Scotland, Switzerland, and other mountainous regions. In the mountainous parts of Great Britain, for instance, isothermals so drawn, had we the data to do it, would be neither more nor less than contour lines. The fault of the chart consists in not keeping this distinction in view. Thus, in the Rocky Mountains, the isothermal of 44° passes over Denver, the mean temperature of which, on an average of three years, is 51°0; and in the Alleghany Mountains, Ashville, N.C., lies within the closed isothermal of 48°, but its mean temperature on an average of four years is 54°. In constructing such charts, mountainous regions should be altogether kept clear of the isothermals. For the vast plains of the States the chart is a valuable one, and the tracing of the influence of the lakes, river basins, and more marked contour lines on the course of the isothermals, is very instructive. After a somewhat minute examination of the lines, we have only to note, in way of criticism, that the isothermal of 44° is drawn too far northward in the region of Lake Ontario; the mean temperature of Toronto being 44°2 and Kingston 42° 8, showing that it should be drawn nearly along the northern shore of that lake.

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.]

Sub-Wealden Exploration

IT must be with great regret that geologists see the announce. ment made in NATURE, vol. xi. p. 236, that all the efforts to clear the bore-hole at Netherfield have been unavailing, and that it has to be abandoned. But is it advisable, I would ask, that another should be commenced on the same spot? When the

1,000 feet were clear, it seemed desirable to go deeper, as no one could tell how soon the Paleozoic rocks would be reached; but surely if it is to be recommenced de novo, it would be better to select another site. We already know from the boring nearly all we care to know-that we are not there on the axis of Paleozoic rocks, but in a basin.

The Kimmeridge clay, which is 240 feet thick at Marquise, becomes thicker in a south-westerly direction to 360 feet near Boulogne, and now we know that it reaches some 660 feet at a point six times the distance in a direction W.N. W., which thickening is continued to its outcrop under St. Alban's Head, though it thins again to the west. The coral rag which occurs in the Boulonnais is here gone through; it sets in again near Weymouth, and since this is followed in the former locality by 385 feet of Oxford clay and Lower Oolitic rocks, we may expect at least 600 feet of them at Netherfield before we reach Paleozoic rocks, which will be almost certainly lower than the coal.

The facts so far ascertained by the boring prove, therefore, as much as we could wish to know, except the age of the Paleozoic rock when met with, if that could be discovered from the small core. They show that the spot is to the south of the axis we are seeking, and the thickening of the Kimmeridge clay would tend to throw that axis some considerable distance to the north.

No such Jurassic beds occur at London, Harwich, or Calais ; but the Cretaceous beds directly overlie the Paleozoic. The conditions on one side and on the other are therefore very different. To the north the Paleozoic rocks are spread out not so far from the surface, and on this side only have the coal measures been proved; to the south they are scooped, or dip, into a hollow, in the midst of which is the Netherfield boring, and which hollowing out would have removed all coal-bearing strata, even if originally there.

This verification of what might have been argued from facts already known has been given us by the Sub-Wealden boring; what more can it do? It has proved that our interest is in localities further to the north, as Messrs. Godwin Austen and Prestwich supposed it to be. Doubtless no better locality, near Brighton, could have been chosen; but if what is essentially another boring is to be made, why not select a locality from which some fresh information might be obtained? A bore at Folkestone would probably pass through little or none of the Jurassic series; but the best place for a new experiment would be somewhere in the neighbourhood of Goring, which would be on the line both of Mr. Godwin Austen's and Mr. Prestwich's supposed range of coal-fields, and would afford a crucial test whether the Paleozoic rocks are really continuous between London and Frome at an accessible depth; and this is what we most want to know.

If a new boring is put down at the same place, it would be well to have a third for some small depth, in order to obtain the dip by a comparison of corresponding beds. Jan. 25

J. F. BLAKE

The Rhinoceros in New Guinea

I AM quite of your opinion that the occurrence of a rhinoceros in New Guinea is very seriously to be doubted (see NATURE, vol. xi. p. 248), but I beg leave to mention a report of a very large quadruped in New Guinea, which I got from the Papuans of the south coast of the Geelvinks Bay. When trying to cross the country from there to the south coast, opposite the Aru Islands, -in which I did not succeed, but only saw the sea-shore at a great distance from the height of a mountain chain (I afterwards succeeded in crossing the continent of New Guinea from the Geelvinks Bay more to the north, over to the Maclure Gulf),—and when hunting wild pigs along with the Papuans, they told me, without my questioning them, of a very large pig, as they called it, fixing its height on the stem of a tree at more than six feet I could not get any other information from them, except that the beast was very rare, but they were quite precise in their assertion. I promised heaps of glass pearls and knives to him who would bring me something of that large animal, but none did. I cannot suppose, so far as my experience goes, that the Papuans are remarkably prone to lies; notwithstanding I seriously doubted the existence of such a large "pig; " and as the sons of that country are very superstitious, and see ghosts and absurd phenomena everywhere, I may just mention as an example, that when I shot, on the same hunting party, a specimen of Xanthomelus aureus, that most brilliant gold-orange Bird of Paradise, they said they could not kill this bird, because it would lighten and thunder when they did. I booked that report as an

efflux of their lively imagination, though not without discussing in my diary the possibility and significance of the occurrence of a large quadruped in New Guinea.

It is true this statement does not strongly support Lieut. Smith's aperçu, but the one gains a grain by the other; I mean, the probability of the existence of a large quadruped in New Guinea increases a shadow.

The other "fact" mentioned by Mr. Walker (1.c.), concerning the skins of a brilliant red Bird of Paradise, which were obtained on the north-east coast, is an interesting fact indeed, because it appears to confirm M. d'Albertis' discovery of Paradisea rag giana on the south coast. It would be most valuable to compare the skins of the red Bird of Paradise from the north-east and the south coast, or at least those from the first with the coloured figure given by Mr. Elliot in his Monograph of the Paradiseidæ, to become sure of their identity. At all events, if Von Rosenberg maintains (see Noll's "Zoologischer Garten," January 1875), that P. raggiana is an "artificial" skin, his assertion is strongly to be repudiated. "Similar frauds" he pretends to have seen in New Guinea, an assertion which is the bolder and the more inconsiderate, as he has not had under his eyes d'Albertis' skins. A. B. MEYER Dresden, Feb. I

I WAS no doubt wrong in speaking of the occurrence of the rhinoceros in Papua as a fact without the qualification "if con firmed;" but I wrote in a hurry.

From the details supplied by Mr. Smith, which I annex, I think there is at least a very strong probability that there is a rhinoceros in Papua, and the object of my letter will have been attained if it causes explorers on the north coast of that island to look after it, and at the same time places Mr. Smith's name on record as the discoverer of its indications.

"1. The heap of dung first seen, which was quite fresh (not having apparently been dropped more than half an hour), was so large that it excited Mr. Smith's curiosity, and he called Captain Moresby to see it. Neither of them knew to what animal to assign it. Quantities of dry dung were afterwards seen.

2. Shortly afterwards, the Basilisk being at or near Singa pore, Capt. Moresby and Mr. Smith paid a visit to the Rajah of Johore, who had a rhinoceros in confinement. Mr. Smith at once observed and pointed out to Capt. Moresby (who agreed with him) the strong resemblance between the dung of this animal and that they had seen in Papua.

'Seeing there is no animal known in Papua bigger than a pig; seeing also that Mr. Wallace has pointed out the African affinities of many of the animals in the islands he associates with Papua; seeing also that the Sumatran rhinoceros approaches the African in having two horns and no shields or folds in its hide, why should there not be a rhinoceros in Papua approaching still nearer to the African type, or furnishing an additional piece of evidence in favour of Mr. Wallace's hypothesis of a submerged continent connecting New Guinea, &c., with Africa?" Chester, Feb. 1 ALFRED O. WALKER

Geology and the Arctic Expedition IN the last number of NATURE, p. 253, it is stated that the appointment of a botanist and zoologist has been recommended by the Royal Society, but it does not appear that anything is being done for geology.

It may be deemed by some an erroneous view of the matter, but I am quite disposed to believe that if the necessary arrange ments can be made, geology is more likely to derive important results from this expedition than any other branch of science.

We are continually having additions to the long series of papers on the Glacial Period, but the still more remarkable warm period in the extreme north is altogether neglected; no one seems capable of even suggesting a probable explanation. It is quite evident, in the first place, that we want more facts, and there will probably never be a better opportunity of obtaining them than in the course of the new expedition. Carefully conducted researches would probably reveal the existence of a still further extension than has hitherto been suspected of the fossiliferous Miocene beds which have already yielded such valuable results.

Even now, it can hardly be doubted, that just before the advent of the cold period, a magnificent flora, which woul require at least as much light and warmth as we now enjoy in England, was flourishing in luxuriance as far north as the 75th parallel. The contemporaneous fauna may now be discovered, and

"Uranometria," but we find it in the catalogue to Heis's Atlas as a 67. In the excellent chart of the seventh hour of R.A., by Fellöcker of Kremsmünster, forming one of the series prepared under the auspices of the Berlin Academy of Sciences, we find it marked only of 89 magnitude. There is consequently sufficient evidence upon record to justify the appearance of this star in our catalogues of suspected variables, even if it be not considered decisive as to variability. Yet the object seems to have been generally overlooked of late years. We are nevertheless able to state that in 1873 and 1874 small fluctuations of brightness could be detected, and may recommend it to the attention of observers who are more especially interested in the variable stars. The position for the commencement of the present year is in right ascension, 7h. 23m. os., and polar distance, 91° 39′. A star of 9'10 magnitude precedes it about 4 seconds in R.A., and about ' north. The colour is a full yellow or light

orange.

(2). Mira Ceti, according to the formula of sines in the last catalogue of variable stars, issued by Prof. Schönfeld, will attain its maximum in the present year on February 24. The minimum determined in the manner adopted by this eminent authority will fall on September 30. The first maximum of 1876 is on January 17.

(3), B Cygni was indicated as variable by J. Klein, of Cologne, from a series of careful observations by himself, between July 1862 and November 1863, and Schönfeld includes the star in a provisional list prefixed to his catalogue of 1875, ascribing a variation between 33 and 3'9 mag. to the brighter component of this beautiful object. It is not the first time that variability has been suspected in one component only of a double star. We are able to state that last August, ẞ Cygni, as a naked-eye object, certainly looked dimmer than we had often remarked it. THE ZODIACAL LIGHT has presented itself on each clear evening since our last, but most conspicuously on the 31st ult. It was then distinctly traceable to Arietis, and at best views a fainter offset appeared to extend very nearly to the Pleiades. The axis passed a few degrees south of Piscium. The intensity of light was certainly more than twice that of the Galaxy in its brightest part between the constellations Cassiopea and Cygnus.

ENCKE'S COMET.-The re-discovery of this body is not yet announced, but it will be strange if it is not detected with the larger telescopes before moonlight interferes in the evening. In 1842, when the perihelion passage occurred at the same time as in the present year, it was observed with the Berlin 9-inch refractor on Feb. 8th; much more effective instruments, however, are now common, and if the comet's constitution has remained unchanged, we might have expected observations in January.

HALLEY'S COMET.-In our "Astronomical Column," next week, we shall give the principal results of the late M. de Pontècoulant's calculation of the perturbations of this comet (so interesting, especially to English astronomers) during the actual revolution, and describe the path in the heavens which his work indicates for the year 1910.

Wollaston, T. Young, Kater, Baily, Sir J. Herschel, Earl of Rosse, Lord Wrottesley, Sir E. Sabine, and lastly, but most of all, W. H. Miller and the present Astronomer Royal, we need scarcely say there should be much in this Annual Report worthy of our notice. We confine our notice here to that part of the business of this department which is most likely to interest our readers, without referring to its various official or State duties.

One part of the business of this department appears to be the conducting of comparisons and other operations with standards of length, weight, or capacity, in aid of scientific researches or otherwise. Amongst such comparisons we note the determination of the lengths of two Russian pendulums for use in the Great Trigonometrical Survey of India, in ascertaining by combined astronomical and telegraphic observations the exact position of a number of fixed points on the earth's surface. Standards were also verified for the Governments of Canada and India, for special use.

Chemists and physicists are glad to rely on the accuracy of their measures or weights, as compared with our own or foreign standards, and to be assured of the constancy of the units employed in their researches. This part of the business of the Standards Department would appear therefore to be of practical use to those whose researches require such accuracy. To maintain uniform the weights and measures of our laboratories is not only aiding individual research, but facilitating the exchange of scientific experience.

Many additional instruments are stated to have been added to the valuable collection of comparing apparatus deposited in this department: one of these is the new powerful air-pump, by Deleuil, to be attached to a vacuum balance. During the preparation of new gold and silver standard trial-plates, elaborate experiments were made by the chemist of the Royal Mint, on gold and silver alloys, reference to which is made in the special Report of These experiments are referred to more particularly the Warden of the Standards appended to the Report. in the paper by J. Norman Lockyer, F.R.S., and W. Nov. 20, 1873, on the quantitative analysis of certain Chandler Roberts, read before the Royal Society on alloys by means of the spectroscope.

Attention is called in this Report to the teaching of weights and measures in schools. There is no doubt that a large number of obsolete and unnecessary weights and measures are used in school text-books. The teaching of the metric system of weights and measures is now abandoned in schools under the authority of the Education Department.

The use of the mirror and electric lamp has been so eloquently demonstrated by Professor Tyndall, that our readers will be glad to see appended to the Report a paper on the employment of a mirror and a ray of light for indicating differences in standard weights, or in measures of length. This paper is a translation of a paper by C. A. Steinheil, read in 1867 at the Imperial Academy of Sciences at Vienna, and is a valuable record of the work of one who spent his life in scientific research.

Also appended to this Report is a short table for the reduction to o° C. of readings of barometers with metric graduations on their glass tubes, based on those coefficients of the expansion of mercury and glass adopted in standard measurements, viz. :

Cubic expansion of mercury. o'00017971 for 1° C. Linear expansion of glass . . 000000886

As an instance of the precision with which measurements are now made, we may refer to p. 40 of this Report, from which it appears that the value of a micrometer was determined at two different periods to be 0.00003181 and 0'00003183 inch respectively; showing a difference of only o'00000002 inch. Such precision may appear to be scarcely necessary except in particular researches. As, however, any error in the production of a direct copy of