THURSDAY, JANUARY 20, 1881 PEDS NORTH AMERICAN PINNIPEDS History of the North American Pinnipeds: a Monograph of the Walruses, Sea-Lions, Sea-Bears, and Seals of North America. By J. A. Allen, Assistant in the Museum of Comparative Zoology at Cambridge. (Washington: Government Press, 1880.) HIS bulky octavo volume forms No. 12 of the miscellaneous publications of the Department of the Interior, United States Geological and Geographical Survey of the Territories, which is under the charge of F. V. Hayden. It is a most important contribution to the life-history of the species of American Pinnipeds, for which the zoologist as well as the merchant may well thank both Mr. Hayden and Mr. Allen. It is not an easy task to analyse a closely-printed volume of nearly 800 pages, but still we trust to be able to give our readers some notion of the general contents of this interesting work. Of the mammals, leading an essentially aquatic existence, the furred and fin-footed group have always had an importance and interest for mankind. The existing Pinnipeds constitute three very distinct families-these are the Walruses, the Eared Seals, and the Earless Seals. The first two are far more nearly allied than are either of these with the third. The Earless Seal is the lowest or most generalised group. The Walruses are really little more than thick clumsy fat forms of the Eared Seal group, with immensely developed canine teeth, and skulls modified so as to bear these. All the Pinnipeds have a high degree of brain development, and are easily domesticated under favourable conditions; they manifest strong social and parental affections, and they defend their young with great courage. They are, almost without exception, carnivorous, mostly feeding on fish, mollusks, and crustacea. While the Eared Seals are polygamous, the males greatly exceeding the females in size, the Walruses and the Earless Seals are thought to be monogamous, and there is very little difference between the size of the sexes. The polygamous species usually resort in large numbers to favourite breeding-grounds, the young are born on dry ground, and are at first unable to swim; while the monogamous forms do not so uniformly resort to particular breeding-grounds on land, and they leave the water only for short intervals. As a group the Pinnipeds are very distinctly characteristic of the Arctic, Antarctic, and temperate portions of the globe; very few range into tropical waters, and only one species can be said to be strictly tropical. While the Seals, Eared and Earless, are abundantly represented on both sides of the Equator, the Walruses are only to be found within the colder portions of the Northern Hemisphere. Of the family of the Walruses but two living species belonging to the genus Odobænus are known, the one, O. rosmarus, being the Atlantic Walrus; the other, O. obesus, the Pacific Walrus. The history of both species is here given at length: first a full synonymy is given; then the general history, accompanied by figures; then habits, products, food, and enemies. Among the figures given are those of Elliott of the head of the Pacific species, which give an idea of the uncouth facial aspect and of the VOL. XXIII.-No. 586 strangely-wrinkled skin; but it is a pity that none of Elliott's representations of an adult form were reproduced from his work on Alaska, published in 1879, and of which only one hundred and twenty-five copies were printed. Capt. Cook's description of this species is still one of the best extant-a species that may soon disappear if the annual slaughter of ten to twelve thousand animals is allowed to continue. The number of genera and species among the group of the Eared Seals has fluctuated immensely even within the last ten years. The views of Gray and Peters have repeatedly changed on this subject, "greatly," the author writes, "in the case of Gray, out of proportion to the new material he had examined." In Peters' latest enumeration he gives thirteen species: five are Hair Seals, or Sea-lions, eight are Fur Seals, or Sea-bears. Mr. Allen enumerates ninetwo with doubt. Five are Hair and four Fur Seals. A good deal of this discrepancy doubtless arose from writers not having learnt to distinguish the sexes, and from their not making due allowance for the great changes in contour and details of structure that result in the skulls of these animals from age. The most striking fact in respect of the distribution of the Eared Seals is their entire absence from the waters of the North Atlantic. The Fur and Hair Seals have nearly the same geographical distribution; but though commonly found frequenting the same shores, they generally live apart. They are about equally and similarly represented on both sides of the equator, but are confined almost wholly to the temperate and colder latitudes. The Hair Seals have coarse hard stiff hair, and are wholly without soft under-fur, the abundant presence of which in the Fur Seals it is which makes their skins so valuable as articles of commerce. The Eared Seals are all gregarious and polygamous. Their breeding-places have received the strangely inappropriate name of "rookeries." The strongest males generally secure to their lot from twelve to fifteen females. During the breeding season the males remain wholly on land, and they will suffer death rather than stir from their chosen spot. They thus sustain for a period of several weeks a continual fast. Steller's account, given nearly a century ago, applies still to nearly all the species. The "sea-fur" of the furriers is obtained from these Eared Seals with the under-fur. Fortunately the destruction of the Fur Seals at the Aleutian Islands, where at one time these seals were killed at the rate of 200,000 a year, has now been placed under rigid restrictions, and the same systematic protection ought to be afforded to them at all their stations. In 1877 Mr. Elliott calculated that the number-owing to the Government regulations— of Seals on the Alaska Islands had increased so as to leave 660,000 breeding females to be added to the original stock, and that the total number would not be much less than 1,800,000. The description of the Earless Seals forms nearly one half of the volume. The technical history of the group is given at length and is most interesting. The genus Phoca of Linneus embraced four species now placed in four distinct genera and in three families. Since then 103 distinct specific and varietal names have been bestowed upon what our author considers as sixteen species. These are located in three sub-families and placed in N 4644 eleven genera. Copious synonymic details are given, Of the restricted genus Phoca, three-P. vitulina, P. Groenlandica, and P. fætida-are marine, and frequent the northern oceans, never descending anywhere near to the equator. A fourth, P. Caspica, is found in the Aral and Caspian Seas, and a fifth, P. Sibirica, is from Lakes Baikel and Oron. Monachus albiventer occupies an intermediate position (Mediterranean, Madras, and Canary Islands) between these northern forms and the Antarctic species, such as Macrorhinus leoninus, Ogmorrhinus leptonyx, Ommatophoca rossi, and the like. All the species have strong social instincts, and are almost unsurpassed in their affection for their young. Most of them are gregarious; few of them are in the least ferocious; they are in general patient and submissive creatures, quite harmless to man. Fond of basking in sunshine, they spend a good deal of their time out of the water, on bank, rock, or ice. They are very voracious, eating fishes, or in lack of these, mollusks and crustacea. Strange though it may seem, the young seals take to the water reluctantly, and have to be actually taught to swim by their parents. The young of some species remain on the ice until they are from two to three weeks old, or until they have shed their first soft woolly coat of hair; their cry is more of a bark than a roar; that of the young is a kind of tender bleat, putting one in mind of the cry of a young child. Dr. Murie (Proc. Zool. Soc. London, 1870) has characterised three distinct modes of terrestrial locomotion among these Seals, from which it would appear that the Phocine Seals generally have considerable power of movement upon land. The Seal-hunting districts are described at length; the oil and skins of these Seals having a large commercial importance. The Dundee sealers took in 1876 nearly 40,000l. worth. The habits of the various species form a most interesting portion of this division of the volume, and the author seems to have ransacked every treatise on the subject so as to make his own complete. This his tory of the North American Pinnipeds will long remain a perfect monograph of a valuable and important group of mammalia. CATALOGUE OF NEWCASTLE LIBRARIES Newcastle-upon-Tyne Public Libraries. Catalogue of the Books in the Central Lending Department. Compiled by W. John Haggeston, Chief Librarian. (Newcastleupon-Tyne: 1880.) N O portion of a book draws more heartfelt commendation or more earnest rebuke from a critic who has read it, not for the purpose of criticising, but for that of using its information, than the index. Only the reader who picks up a book for recreation and amusement feels at all independent of it; and even he appreciates its importance if any future reference is required. And if a good table of contents is so requisite in the case of a single book, how far more. so must one be in a large library. We have here a new catalogue of a new library, a selection of 20,000 volumes of books chosen for their readable value only (which perhaps justifies the omission of all dates of publication of the books, which would be a fault in a catalogue of most libraries), and consequently we may look to it as a model of what a catalogue should be. And we shall not be disappointed. It is drawn up on the same scientific principles worked out so fully in Dr. Billing's catalogue of the U.S. Surgeon-General's Office, which we noticed lately; and these so well worked out too, that really it is a table of contents of the library; the matter contained in the volumes of the latter as well as their titles are all laid before us. Each work is entered under the author's name, under the title, and, in cases where that title is compound, under each of the subjects it may include. Under the heading of each principal subject treated a reference is again given to the work with its library number, and so numerous are these cross references that on an average every volume throughout the library appears four times over. Indefinite titles are rectified by a summary being given, in a smaller type, of the matters discussed. Catalogues which limit themselves rigidly to the contents of the title-page abandon all attempts at completeness, since many titles do not even pretend to express the subjects of the book (need we cite Mr. Ruskin's ?), and many equally fail in the attempt. As the field of literature increases, and not even a librarian can keep himself acquainted with the ground gone over by all the books under his care, a subject-catalogue as well as an author- and title-catalogue becomes a necessity, and, if it is well drawn up, though it inay cost both money and time, they will be well spent. Volumes that appear unattractive enough to the general reader, and are far too numerous for the ordinary student to search through, become suddenly, through a subject-catalogue, of the greatest value to both of them. The books in a library whose contents are thus laid open to its frequenters will be read with profit much greater than would a considerable fraction more books whose title-page was all the introduction their readers had to them. And the saving of time when it is completed will be immense. It will save the time of the librarian by preventing hundreds of inquiries being made at all, and still more by strengthening the hands of his assistants, who will be capable of working his catalogue to the utmost and answering a very large proportion of such inquiries as are made by readers who may be awkward at it; it will save the time of the busy man, who wants his information at once; it will save the time of the student who wants the most recent information which he can get; and it will save the time of all by making fewer changes of books necessary. All this is doubly important in a Free Library, because, as any one taking an interest in these institutions will have marked, those of its readers who do not confine themselves to novels seldom take out books for the mere pleasure of reading, as the higher classes do. Reading has not yet become a recreation to them, but they go to the library as to a great encyclopædia to get information on certain subjects, often of the most technical character; and a catalogue that directs them to the very book they want doubles and trebles the value of the library to them. They have no time to read all the critiques and résumés of new books with which the press teems, and which make the style and contents of many such works familiar to readers of periodicals who may never have seen the works themselves. Where hundreds go in an evening for books it is impracticable to allow them access to the shelves of the library to select them; while in an ordinary bare list of titles it is impossible for them to judge which book in a column will be found the one most to their require ments. Like Dr. Billings, our Newcastle librarian has fully worked out a most important branch of a subject-catalogue. Magazine literature in these days has become far too important to be treated by either a thrifty librarian or an inquiring student as "fugitive" and "ephemeral." All the newest science now appears first in journals, and all leaders of thought give their first expression of it in magazines and reviews. In this new catalogue therefore we are much pleased to see that not only is each volume of all important periodicals entered separately with its list of articles, but, as we have said, under the head of each subject a reference is given to all of such articles as bear upon it. By this means students who have read a standard work published a few years ago upon any subject will be not only guided but stimulated into reading the latest researches or theories which these publications contain. It is perhaps going beyond our subject, but we cannot help noticing how convenient for this important purpose a card-catalogue at a library is; in which cards containing the subject of each article down to the last number of all the magazines have been dropped into their places. Such an arrangement would make many students feel a printed catalogue to be ancient by the time it was published. The selection of books as a whole is admirable-though of course few selections have been made under such favourable circumstances. We are rather surprised in so large a list to note the absence of books like Boyd Dawkins's "Cave-Hunting" and "Early Man in Britain,' Clifford's "Lectures and Essays," Croll's "Climate and Time," Moseley's "Naturalist on board the Challenger," and Sir Wyville Thomson's book; Hæckel's "History of Creation" and "Evolution of Man"; Schliemann's "Troy" and Cesnola's "Cyprus"; Wallace's "Geographical Distribution of Animals," &c. And if some of these are so costly as to be confined to the Reference Library, as is probably the case here, still we are sorry to miss Wallace's "Tropical Nature," and R. Jefferies ("The Gamekeeper at Home") with his series of books teaching men to open their eyes as they move about the fields and lanes. The printing is a credit to both printer and editor. It is almost as funny as the "Ingoldsby Legends" to read "Life and Remains of Dean Hook," by Barham! but it is plainly a slip, and the smallest errors are very scattered. The Rules and Regulations are clumsy to enforce, which indeed will probably not be attempted, at any rate for long. The annoyance of having to get a guarantor practically shuts out many whose hitherto idle life might have taken a fresh start if books had been put into their hands freely. We have been very pleased to see that several large libraries have done away with this irritating system without any loss of property, and it seems a step backwards when a new institution like this starts with more rigid and inconvenient rules than many others. Indicators are capital things in libraries to which each reader goes for his own book as at a university, but only very few of the hundreds who exchange books every night at a flourishing Free Library are at all able to work with them. Children are the usual messengers, not high enough to consult an Indicator of 20,000 volumes. It is an unmerciful rule that borrowers should return their books personally, and a downright unreasonable one that every book must be returned in a fortnight (Rule 17), NOT to be re-issued the same day (Rule 16), although we are told (p. vi.) that three-volume works are issued complete. Few Free Library readers can get through 600 or 800. pages in a fortnight. And surely it was not necessary to threaten each person who consults the catalogue with imprisonment with whipping if he defaces a book! It may be necessary to make such Draconian laws, but they should be brought forward to intimidate gross offenders, not flourished in the face of all whom we wish to attract. Such severe rules repel sensitive people, while from their very familiarity they lose their effect on the careless. OUR BOOK SHELF Botanische Jahrbücher für Systematik Pflanzengeschichte und Pflanzengeographie. Herausgegeben von A. Engler. Erster Band, zweites Heft. (Leipzig: Wilhelm Engelmann, 1880.) THIS part includes four papers. The first is by W. O. Focke, on the natural divisions and geographical distridiscussed are:-1. Mode of growth or habit. 2. Forms bution of the genus Rubus. The characters chiefly of leaf which are very numerous: the duration of the leaf being also variable. 3. Characters derived from the stipules, which are considered of great value. 4. Inflorescence; and 5. the Structure of the flower. The number and size of the parts of the calyx and corolla vary, as also the colour of the corolla. The stamens vary in closely allied species, and while most of the species are hermaphrodite, some are unisexual. The structure of the gynoecium is very varied, the number of carpels being five or six in some, as in R. dalibarda, or above 100, as in R. rosafolius. The hairs (trichomes) on the different parts of the plant are very numerous and remarkable for perhaps some Solanaceae, approaching the Rubi in this the variety of structure shown; no other group, except particular. In regard to the geographical distribution the most important points are:-1. The characteristic difference in the Rubi of Eastern Asia and Europe. 2. The predominance of European forms in the Atlantic, and of East Asian forms on the Pacific side of America. 3. The occurrence of south Chinese and north Indian types in Mexico and Peru. These peculiarities Focke would explain on geological grounds. The second paper is by Franz Buchenau on the distribution of Juncaceae over the world. The author gives a complete list of the species of the genera Juncus : Luzula, Rostkovia, Marsippospermum, Oxychloë, Distichia, and Prionium, and a table showing their distribution into regions nearly corresponding to those of Grisebach. Koehne, in the third paper, gives the first portion of a monograph of the Lythracea, including a key to twentyone genera. He admits and then describes thirty-one species with numerous varieties of Rotala (Ammania, Linn., Bentb., and Hooker). The last paper is by Engler. Contributions to the knowledge of the Araceæ, in which he describes some new Araceæ from the Indian Archipelago and Madagascar, and also directs attention to the cultivation of Zamioculcas Loddigesii from the detached leaflets of the remarkable pinnate leaf of the plant. A swelling occurs at the base of the leaflet, and in a few days a small tuber is produced which develops two buds, below each of which roots are formed. The plant has been propagated in this way by Herr Hild of the Kiel Botanic Garden. The Fishes of Great Britain and Ireland. By Dr. Francis Day, F.L.S., &c. (London: Williams and Norgate, 1880.) THIS work is to be issued in nine parts, of which the first, containing sixty-four pages of text and twenty-seven plates, is now published. Waiting until the completion of the work for a more extended notice, we may for the present mention that in it the author purposes to give a natural history of the fishes known to inhabit the seas and fresh waters of the British Isles, with remarks on their economic uses and on the various modes of their capture, and that an introduction to the study of fishes in general is promised. The synonymic lists of the species are given in great detail; the descriptive diagnoses treat of internal peculiarities as well as of external form; a good many interesting details appear under the headings of Habits, Means of Capture, Baits, Uses. The plates are from drawings by the author, and are very excellent. A Manual of the Infusoria. By W. Saville Kent, F.L.S. (London: David Bogue, 1880.) THIS Sometime promised work has now advanced so far in its publication as the third part; when completed it will merit a somewhat lengthened notice, as the most important work on the subject which has issued from the British press. It is intended to include a description of all known flagellate, ciliate, and tentaculiferous Protozoa, British and foreign, and an account of the organisation and affinities of the Sponges. Each part (roy. 8vo in size) contains over 140 pages and eight plates. The general get-up of the work is magnificent, rather too much so for the poor student, already weighed down by the burden of the parts of Stein's " Infusionsthiere," but very pleasant for the book fancier, and forming an imposing shrine wherein to inclose the records of these early-life forms. The first five chapters (pp. 1-194) are introductory, A Complete Course of Problems in Practical Plane obtained; in Prop. 212 the letter E is made to do double Bericht über die Thätigkeit der Botanischen Section der MOST of the papers in this part are in abstract; a few 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 Editor urgently requests correspondents to keep their letters as short as possible. The pressure on his space is so great that it is impossible otherwise to ensure the appearance even of communications containing interesting and novel facts.] Dr. Carnelley's Hot Ice THE remarkable observation made by Dr. Carnelley that ice in a vacuum is very permanent, even though surrounded by and apparently in contact with very hot bodies, has caused him to suppose and maintain that the ice itself is at a high temperature; a supposition which has been apparently confirmed by preliminary calorimetric determinations. This proposition has naturally met with a good deal of scepticism, and certainly requires ample and cautious verification; but I venture to think that there is nothing in it contradictory to our present knowledge of the properties of matter, though if verified (as, for the reasons to be stated, I fully believe it will be) it constitutes an important addition to that knowledge. The notions which have occurred to me have made the essential part of the phenomenon so much clearer to myself that I fancy they will not be uninteresting to your readers. By the term "vapour-tension" at a given temperature I mean, as I believe is usual, the pressure at which a liquid and a vapour can exist permanently together at that temperature, or the maximum pressure which the vapour is able to exert at that temperature, or the vapour pressure under which a liquid ceases to evaporate, or the total pressure at which it begins to boil. By the term 'boiling-point" I mean the temperature of a liquid. under a total pressure equal to its vapour-tension. Now in order that a solid may sublime or pass directly into the vaporous condition without melting, it must be either at a temperature below the melting-point, so that no liquid attempts to form, or else at such a temperature that any liquid formed shall instantly evaporate; which it would certainly do if it were above the boiling-point, that is if the total pressure on it were less than the vapour tension. THIS is a cheap manual, the cost of which can be easily met by any artisan desirous of studying the subject, while at the same time its contents enable it to fully satisfy the wants of all examinees in first, second, and third grade and similar papers of the Science and Art Department Examinations. The figures are very clearly drawn, well showing given, constructional and required lines; the form of the page enables four propositions to be fully treated of with the accompanying figures in four spaces on each page. In the constructions we do not look for novelty, but we have conciseness and great clearness generally prevailing. Here and there elegance of expres-sion is sacrificed to brevity ("for all the Government A solid, under either of these circumstances, gives off vapour examinations, the requirements of which this is a text-proportional to, the supply of heat; for there is no definite subfrom its free surface at a rate depending on, but not necessarily book, the same rules will apply, with exception of Nos. I and 6"). We have detected only three points which call for our notice; in Prop. 12 it strikes us as being simpler to use the same radius throughout, thus doing away with the necessity of taking two cases, as Mr. Palliser does; in Prop. 37, note, it is necessary to add how the point is liming point for a solid, any more than there is a definite evaneed not remain constant. When a liquid is evaporating, the porating point for a liquid, so that the temperature of the solid more you heat it the faster it evaporates, but not at a compen. sating rate, and the temperature rises as well: if this be true for a liquid, much more will it be true for a solid, whose evaporation is always more encumbered, partly, no doubt, because its evaporating surface is a fixture. The only limit to the rise of temperature of a liquid is its boiling, but if this be prevented it may get superheated; and, (unless the solid boil (i.e. disintegrate internally) it can become superheated to any extent. The possibility of this internal disintegration we will examine directly, but at present we will consider it practically nil. Let us grant then that a subliming solid always rises in tempe. rature if heated at a sufficient rate, and Dr. Carnelley's proposition follows. We have seen that no liquid can exist at temperatures below its freezing- or above its boiling-point, so that if we wish to prevent the possibility of its existence, we need only make these two points coincide. This can always be done by diminishing the pressure, for the boiling-point of all substances is greatly affected by changes of pressure, while the freezing- oint is only slightly altered, and even, in the case of ice, in the opposite direction. Start then with the solid below its melting-point, and reduce the pressure on it till the boiling-point coincides with, or passes below the melting-point. There is now no region where liquid can exist, and the solid must therefore sublime; but, by our supposition, a subliming solid if heated will get hot, hence the solid may now assume any temperature you please; and the hotter it gets the more pressure may be brought to bear upon it without causing it to melt, i.e. the pressure may be allowed to increase to anything short of the vapour-tension at the new temperature. If heated sufficiently, then the whole atmospheric pressure may be let in, and no melting will occur. All that is necessary is that heat shall be supplied at a sufficient rate to compensate for the rapid evaporation (which however will not be so rapid as in the vacuum), and to prevent its temperature falling to the boiling-point; for if it reached this, part (or all) would quickly liquefy, and the whole fall to (or towards) the melting-point. Thus we have the remarkable proposition that if, by the process of lowering the boiling-point to coincide with or pass below the melting point, we manage to get ice across the gap which ordinarily separates these two points, it may be heated to 120° or to any other temperature; and that when at 120° it will be permanent, and will not melt even under the whole pressure of the atmosphere. To prevent its melting you must keep on heating it: if allowed to cool to 100°, five-eighths of it will be instantly crushed to water, and the whole will be at o° (assuming, what is not likely to be correct, that the specific heat of hot ice is ). There is still the question of the possibility of internal melting or sublimation to be considered. Now I suppose that if a solid is perfectly homogeneous, a change of state in its interior would with great difficulty occur, and the solid might readily be superheated. But an excess of pressure at any point, such as would be produced by a bubble of air, would readily determine a melting-centre. In Prof. Tyn dall's ice-flower experiment the nuclei are probably minute bubbles of air, and the ice walls of the cavities so produced are subject to the pressure of this air in addition to that of the vapour; and accordingly melting sets in and spreads. But Dr. Carnelley's ice is formed in vacuo, so that no air-bubbles are possible, and the only nuclei that can properly exist are little bubbles of enclosed vapour; and these, I imagine, can scarcely be absent. Let us inquire then what can happen in the case of one of these bubbles when the temperature of the ice is raised either by radiation or conduction. Initially, while the temperature is constant, the vapour is saturated; but no liquid is formed because this temperature is below the melting-point. When heat is applied, the ice, being less diathermanous than the vapour, will get heated first, and so long as the temperature keeps rising it will always be a little hotter than the vapour, which consequently is not quite saturated, and the pressure it exerts is less than the "6 vapour-tension" (ie. the temperature is above the boiling point), and no water can be formed. The cavity will of course enlarge by sublimation, but very slowly, much more slowly in fact than outside, if a vacuum is there artificially maintained. But if cooling be permitted the ice will cool the fastest; and the vapour at once becomes over-saturated and condenses. The temperature is now below the boiling point, and liquefaction instantly sets in and rapidly spreads, the ice consuming its own heat in the process. Internal disintegration therefore will not occur while the temperature is rising, but it will set in at a great pace if it be allowed to become stationary or to fall, unless there be an utter absence of nuclei. If the temperature rises very high the pressure of the internal vapour will of course be great, and ultimately might even be able to burst the ice, but this would scarcely occur under several atmospheres. It would be interesting if Dr. Carnelley would kindly try the following experiments : 1. Heat ice in vacuo with a pressure gauge, and, still heating it, stop the passage to the condenser so that the pressure is allowed to accumulate, and note the pressure and temperature when collapse occurs. 2. Heat ice up to any temperature, and, still maintaining a good vacuum, remove the supply of heat, and see if the ice does not collapse. 3. Heat the ice up to 120°, and, still heating it, let in the atmosphere gently (but make the air come in through hot pipes, or it will melt the ice), and see if the ice does not last rather longer than it would have done in the vacuum, because the evaporation will be more obstructed. But if the second experiment succeed, the temperature must never be allowed to fall much or to remain stationary long. Finally, it is important to point out explicitly that the Carnelley experiment has no bearing on the change of the melting-point of ice with pressure. Our knowledge on this point remains as it was, viz. de that the value of about zero centigrade is dp '0071; that is to say, the melting-point rises and falls about '0071° centigrade per atmosphere of pressure decrease or increase. Of course this number is not absolutely constant, but its variation with pressure is very slight, and moreover has no bearing on the Carnelley experiment, as was naturally but erroneously supposed by Prof. Pettersson in the Berichte (18), and I believe also by Prof. Ayrton at the Chemical Society, though I had not the pleasure of hearing his remarks. University College, London OLIVER J. LODGE Note. With reference to the above second experiment and the reasoning which suggested it, it is important to remark that I have all along assumed that the vapour-tension of ice at any temperature is precisely the same as that of water at the same temperature. But Prof. Foster considers it possible that the vapour-tension of ice may be less than that of water, and would hence explain the permanence of vapour inside an ice-cavity without attending to whether the temperature were rising or falling, This would be a most provided it were not falling too fast. important fact to discover and verify; but I think the Carnelley experiment in its present form does not inform us concerning its truth or falsity. Another thing it may be interesting to note is the rate of variation of boiling-point with pressure at different temperatures, which can be calculated on thermodynamic principles (after Prof. James Thomson) from empirical data for the latent heat of steam, and for the density of saturated steam at any tempe. rature, It is, at the temperature and the pressure p, de 02 dp 273X 0008 X (796′2 — ·695 0) JP a fraction which has the value 28 at 100° C., and 2180 at 0° C. : +796'2 ( - ) }, On the Spectrum of Carbon I 373 I HAVE a great respect for Dr. Watts's spectroscopic work, nevertheless the experiments he has described in NATURE, vol. xxiii. p. 197, appear to me singularly inconclusive for the purpose for which he has adduced them. How could any one expect to get a tube of gas free from hydrocarbons when the joints were of india-rubber and melted paraffin? I have long since found it necessary to forego rubber joints if I would exclude hydrogen. Salet has shown that the hydrocarbons from the blowpipe-flame used in sealing in wires, &c., and the last traces of dust, can only be removed from tubes by burning them out in a current of oxygen. But more than this, I have found |