signed. Unfortunately, however, the utmost uncertainty still prevails both in regard to the size of the ice-sheet and also in regard to the actual extent of the submergence. All that we can therefore do, is to make a rough estimate of what probably was the thickness and extent of the ice, and then to ascertain whether the amount of the submergence theoretically deduced from the supposed quantity of the ice, is anything like an approximation to the generally-received opinion among geologists regarding the probable extent of the submergence.

It has been proved by Mr. Jamieson that in some parts of Scotland the ice-sheet must have at least been 3000 feet thick. Agassiz thinks that in some parts of North America its thickness could not have been less than a mile. The thickness of the ice in Scandinavia and other parts of northern Europe must also have been enormous. What was the probable thickness of the ice in Greenland and other Arctic regions during the glacial period, we are, I presume, unable to form the least conjecture. But to simplify our calculations, let us assume that it was, say 7000 feet thick at the North Pole, and that it gradually diminished in thickness towards the Equator, according to a law, into the consideration of which we need not here enter, so that the upper surface of the sheet should curve exactly the same as the surface of the land underneath. The specific gravity of ice is 92, and the mean specific gravity of the earth, according to the determination of the Astronomer Royal, is 6:56. Hence the specific gravity of the ice-sheet would be to that of the earth as 1 to 7. Consequently, if a sheet of the same density as that of the earth, and 1000 feet thick at the Pole had been substituted in the room of the ice-sheet, it would have produced the same effect. But this would be simply adding 1000 feet to the polar diameter of the globe without increasing its equatorial diameter. But 1000 feet thus placed on one side of the globe which, in the present case, is on the north side, would, of course, shift the centre of gravity 500 feet to the north of its former position, and as the ocean would accompany the centre, there would consequently be a submergence at the North Pole equal to 500 feet. But this is not all; for at the time that the ice-sheet would be forming on the northern hemisphere, a sheet of equal size would be melting off the southern, and this of course would double the effect, and thus produce a total submergence of 1000 feet at the North Pole, and a total elevation of 1000 feet at the South Pole. A sheet 3500 feet thick at the Pole would produce one-half that effect.

The same results would, of course, follow, although the thickness of the ice-sheet at the Poles were far less than we have for convenience assumed, provided that an equal amount of ice be in some way or other placed on the northern hemisphere.

Although the general submergence and re-elevation of the land during the glacial epoch were, no doubt, due to the cause which we have been considering, still there would probably have been local depressions and elevations going on during the period, resulting from other causes, the same as there are at present, and have been in all ages.--I am, yours respectfully,

JAMES CROLL.

3. BIRTH OF A HIPPOPOTAMUS IN EUROPE.

In a paper on this subject read before section D., at the recent meeting of the British Association, at Birmingham, by Mr. Sclater, it was remarked that three pairs of this huge animal were now living in different Zoological Gardens of Europe, viz., in those of London, Paris, and Amsterdam. Though the female in the gardens in London had often shown signs of breeding, and attempts at copulation had been made by the male, it was not believed that conception had ever occurred. In the case of both other pairs, reproduction had taken place on several occasions, but the new-born animal had always perished either from the violence of its parent immediately after its birth, or from incapacity to take food when removed from its mother. The first successful instance of the reproduction of the Hippopotamus in Europe was therefore that which took place at Amsterdam, on the 29th July last, for the details of which Mr. Sclater was indebted to the well known Director of the Zoological Gardens in that city, Mr. G. F. Westerman. Copulation in the present instance had occurred on the 6th and 7th December, 1864, so that the period of gestation was estimated at 234 days, which had been likewise confirmed in the previous cases of reproduction of the same pair of animals. As soon as the birth took place the little animal was removed from the mother, not without some difficulty, as the latter was already on her legs to defend it, and transferred to a separate house, previously prepared for its reception. Here it was now thriving well, and growing fast, taking every day in six or seven meals about two and a half gallons of milk mixed with one-fifth part of water.

4. NOTE ON A SHELL FROM LABUAN.

We have received the following letter:

SIR,-According to Chenu and Woodward, the minute landshell, Scoliostoma is known only as a fossil of the triassic limestone. Having heard a few months ago that there was a curious little shell on an island in this vicinity I one day made a trip to it. The island is a mass of limestone, rising almost perpendicularly out of the sea. It is about 80 yards in diameter, and about 30 feet high, and is full of fissures and caverns, and, like all other islands in this neighbourhood, is covered with vegetation. Upon a naked rock, well protected from the heat of the sun by the surrounding trees, and having upon it here and there scanty patches of moss, I found the shell I was looking for. crawling among the short moss, by the hundreds. I sent home some specimens to Mr. Stevens, of Bloomsbury, but it was not until some time afterwards that I identified the shell with the Scoliostoma of Chenu. I enclose you a few specimens, should they chance to be destroyed by the way, you can procure some more from Mr. Stevens.

The Scoliostoma has never been found in any other habitat hereabouts. The island of Labuan is for the most part sandstone, coal, black sand, and ferruginous clay, but it has not as yet been observed that there is any limestone formation.

I enclose also a portion of the limestone from which the shells were taken, and a piece of crystallized carbonate of lime from the same mass. Should you publish this letter, it may perhaps lead to a curious and interesting disquisition from some one of your more learned readers upon this wonderful little link which connects the present time with the remotest ages.

I am Sir, yours, &c.,

Island of Labuan, 15th March, 1865.

C. C. de CRESPIGNY.

[We have submitted the shells forwarded by our correspondent to Mr. Henry Woodward of the British Museum. Mr. Woodward informs us that the specimens do not belong to the genus Scoliostoma (which is a marine form from the trias), but are closely allied to, if not identical with Opisthostoma, discovered in 1859, by Messrs. H. F. and W. T. Blanford, near Pykara, on the Nilgiris, in Southern India.-ED.]

5. LIST OF PUBLICATIONS RECEIVED.

[Continued from page 456.]

(73.) Proceedings of the Literary and Philosophical Society of Liverpool, during the Fifty-third Session, 1863-64. No. XVIII. London, Longman and Co. 1864,

(74.) Das Vorkommen des Parasit ismus im Thier-und Pflazenreiche. Dargebracht von George, Ritter von Frauenfeld. Wien, 1864. (75.) Rendiconti del Reale Istituto Lombardo di Scienze e Lettere. Classe di Scienze Matematiche e Naturali. Vol. I. Fasc. IX. X. Vol. II. Fasc. I. II. Milano, 1865.

(76.) The Geological Magazine. Edited by T. Rupert Jones, F.G.S. Longmans, London. Vol. II. Nos. 6, 7, 8, 9.

(77.) Memorie del Reale Istituto Lombardo di Scienze e Lettre, Classe di Scienze Matematiche e Naturali. Vol. X. I. della serie IV. Fasc. I. Milano, 1865.

(78) Revision der bis jetzt bekannt gewordenen Arten der Familie der Börstenthiere oder Schweine. Von Dr. L. S. Fitzinger. Wien, 1864.

(79.) Palæontographical Society's Memoirs. Vol. XVII. Issued for 1863. London, 1865.

(80.) Homes without Hands. By the Rev. T. G. Wood, M.A., F.L.S. Part XX. London, Longmans and Co.

(81.) A Course of Lectures on Hydrophobia; its History, Pathology and Treatment. By T. C. Shinkwin, M.D., M.R.C.S.L. Dublin. (82.) On the Ultimate Nerve-Fibres distributed to Muscle and some other Tissues, with Observations upon the structure and probable mode of action of a nervous Mechanism. Being the Croonian Lecture for 1865. Delivered by Lionel S. Beale, M.B. F.R.S. From the Proc. Roy. Soc., May 11, 1865.

(83.) The Antiquity of Man: an Essay read before the Roy. Irish Academy, Jan. 23, 1865. By John Locke, A.B., &c. Dublin, 1865.

(84.) The Declaration of Students of the Natural and Physical Sciences. London, Simpkin, Marshall and Co.

(85.) Report of the Manchester Scientific Students' Association, for the year 1864. With an Appendix, consisting of a Synonymic list of British Terrestrial and Fluviatile Mollusca. By John Hardy. Manchester, 1865.

INDEX.