independent of those which have been made, or may be made, directly on the pressure of aqueous vapour at different temperatures near the freezing-point, both above and below it, very correct determinations of the values of the quantities C, M, and M' can be made, such determinations will lead to more correct evaluations

dp dp'

dt

dt

of and for aqueous vapour in contact in the one case with liquid water, and in the other with ice, than we at present possess. Such determinations, we may presume further, would, if very trustworthily arrived at, conduce to the attainment of a more correct estimate of the density of steam at the freezing-point (or at the triple point) than we now possess. In fact, in connexion with the subject which has been here under consideration, there are various important quantities so connected that improved determinations of one or more of them may lead to more correct evaluations of others.

GEOLOGICAL SOCIETY.

[Continued from p. 315.]

May 14, 1873.—Joseph Prestwich, Esq., F.R.S., Vice-President, in the Chair.

The following communications were read :—

1. "On the genus Palæocoryne, Duncan and Jenkins, and its affinities." By P. Martin Duncan, M.B. Lond., F.R.S., V.P.G.S., Prof. of Geology in King's College, London.

In this paper the author referred to certain minute fossils from the Carboniferous rocks of Scotland, described by himself and Mr. Jenkins in a paper read before the Royal Society, as belonging to the Hydroida, and most nearly resembling the recent genus Bimeria, Wright. He stated that numerous specimens since received from the Geological Society of Scotland threw some further light on the nature of these fossils, and showed especially that in all probability the base is not really cellular, but that the cellular appearance is produced by the growth of the real base of the polype over the cells of the Fenestella on which it grows. The author further described what he believed to be the mode of growth of this organism, as displayed in the new specimens.

2. "Notes on Structure in the Chalk of the Yorkshire Wolds." By J. R. Mortimer, Esq.

In this paper the author described a peculiar structure observable in chalk from Yorkshire and elsewhere, giving it a striated appearance. This structure had been ascribed by Dr. Mackie and others to slickensides. The author adduced reasons for doubting the mechanical origin of these striations, and argued that they are of an organic nature. He ascribed them to corals, and remarked that similar striæ occur in all limestone formations.

3. " On Platysiagum sclerocephalum and Palæospinax priscus, Egerton." By Sir Philip de Malpas Grey-Egerton, Bart., M.P., F.R.S., F.G.S.

The two species of fossil Fishes noticed in this paper were described by the author in the 13th Decade of the Memoirs of the Geological Survey, published in 1872. They are both from the Lias of Lyme Regis. He now described some new specimens which add to our knowledge of their characters. An example of Platysiagum shows the position of the dorsal fin, which is placed very far back, occupying a place opposite to the interval between the ventral and anal fins, and the form of the trunk, which is of nearly uniform depth from the occiput to the base of the dorsal fin. The structure of the dorsal fin was described in detail. The new specimen of Palæospinax priscus shows especially the position of the second dorsal spine, which is placed over the 50th vertebra, the first being on the 16th, the fish thus most nearly approaching the existing Cestracion, which it also resembles in its dentition. In other respects it seemed to be most nearly allied to Acanthias.

4. "On a new genus of Silurian Asteriada." By Thos. Wright, M.D., F.R.S.E., F.G.S.

The specimen described showed the outline of a small Starfish, with a large disk and short rays, in a slab of Wenlock Limestone from Dudley. The outline of the ten rays was described as marked out by the border of small triangular spines, the other plates of the disk and rays being absent. Each ray was terminated by a stemlike multiarticulate process as long as the ray, from towards the extremity of which spring slender lateral processes, giving it a tufted appearance. This Starfish, which is in the collection of Dr. Grindrod, is named by the author Trichotaster plumiformis.

May 28, 1873.-Prof. Ramsay, F.R.S., Vice-President,
in the Chair.

The following communications were read :—

1. "The Glaciation of the Northern part of the Lake-district." By J. Clifton Ward, Esq., F.G.S.

The author stated the leading questions to be settled by his investigation of the northern part of the Lake-district as follows:— The fact of the glaciation of the district being granted, and of this he adduced abundant evidence, the questions that arose were whether the glaciating agent worked from north to south, whether it came from within or from without the district, and finally, whether the agent was floating ice, a system of local glaciers, or an unbroken ice-cap. As the result of his investigation, he maintained that there is no evidence that a great ice-cap from the north ever swept over this district. The ice-scratches trending along the principal valleys, but sometimes crossing watersheds, indicate a great confluent glacier-sheet, at one time almost covering a great part of the district, the movement of which was determined by the principal watershed of the Lake-district. In the part of the Lake-district under

consideration the ice, during its increase, carried forward, from south to north, a great quantity of rocky material. There are no signs in the district of the occurrence of mild periods during the epoch of primary glaciation; but the author thought that the climate had probably become moderate before the great submergence of the land commenced. The author noticed the effect of the submergence upon the results of previous glacial action, and maintained that when the land had sunk 800 or 900 feet there was a recurrence of cold, and boulders were transported by floating ice. Until the submergence reached 1500 feet there was no direct communication between the northern and southern halves of the Lake-district, except by the Straits of Dunmail Raise. From the directions which would be taken by the currents in the sea at this peried, it would appear that boulders may then have been transported by floating ice in some of the same directions as they had previously been carried by glacierice. The extreme of submergence appeared to have been about 2000 feet. The author further maintained that on the reelevation of the district there was a second land-glaciation, affecting the higher valleys and clearing them of marine drift.

2. "Alluvial and Lacustrine Deposits and Alluvial Records of the Upper Indus Basin." By Frederic Drew, Esq., F.G S.

First stating that the alluvium of that country had been noticed by several travellers, especially by Major Godwin-Austen, who had given much important information about them, the author said that he felt the necessity for a careful classification of the phenomena of alluvial deposits; for the want of recognition of the different kinds was likely to lead to incorrect deductions; the classification he proposed was the following:-

I. Loosened material, which consisted of disjointed rocks or loose angular stones, sometimes mixed up with mud, which had been separated and disintegrated, but since that had remained unmoved.

II. Taluses, the substance of which had fallen by its own weight, and not been transported by streams. These were the great heaps of angular matter that were found at the foot of cliffs, with a slope generally of near 35°. A special form was the fan talus, which occurred where the falling matter had either originated from, or collected to, one spot, from which again it spread, and made a partial cone of the same slope as the ordinary taluses.

III. Alluvial Fans.-These were the fan-shaped extensions of alluvial or torrential matter that spread out from the mouths of gorges, where these debouched into a more open valley. They were in form cones of a low angle, commonly 5° or so; they had accumulated by layer after layer on a cone-shaped surface, as shown by the radial sections exhibiting layers of a straight slope, and the chord sections showing curves, which were by the theory hyperbolas. Many complicated phenomena were produced by the denudation of these fans, and the production of secondary ones, some of which were illustrated by diagrams.

IV. Alluvium, which was defined as a deposit which sloped down

the direction of the valley of the stream which had made it, and did not appreciably slope or curve over in a direction at right angles to that.

The alluvium of the country in question consisted mostly of pebble-beds, well stratified; it was common at all heights, from 16,000 feet or more downwards. Sections of some 100 feet thick were to be observed at intervals along the valleys of most of the rivers: one of 500 feet was described as occurring near Sumkiel, in Rupshu; and 200, 300, and 400 feet heights of the alluvial terraces above the rivers were very general.

In a few cases there were wider openings, filled with similar deposits. The tableland of Deosaï, where the alluvium made flats at an elevation of 12,500 and 13,000 feet, surrounded by a ring of mountains 16,000 and 17,000 feet high, was the most remarkable of these.

A special phenomenon was described as now and then occurring in the alluvium, namely a sloping of the alluvial strata, looking at first like false-bedding on a large scale, and, further, a curving or bending of them till they reached round even beyond the perpendicular. This the author attributed to the ploughing of the foot of a glacier against the alluvium that had been formed in front of it by its own streams.

The last class of alluvial deposits would be the lacustrine; but a description of these was reserved for a future portion of the paper.

Summary and Inferences.

There was evidence of a succession of three states:

1st. The cutting of the valleys.

2nd. The accumulation of alluvial matter.

3rd. The cutting down of the streams through that alluvial matter.

Accumulation denotes an excess of supply of material from the rocks (by disintegration) over what can be carried away by the streams.

Denudation, or the cutting down of the streams through their alluvium (the lowering of their beds), denotes a deficiency of supply of material from the rocks as compared with the transporting power of the streams. Hence the author inferred that the period of great accumulation of these alluvial deposits was one of great disintegration of rocks, one of intense frost (in other words, it was the Glacial period), and that the denudation occurred when the cold lessened and there came to be a smaller supply of disintegrated material.

The connexion of various glacial phenomena with the alluvium, such as the one described above, was taken to corroborate the inference that the greater deposits were made during the Glacial epoch.

June 11, 1873.-Prof. Ramsay, F.R.S., Vice-President, in the Chair. The following communications were read:

-

1. "On the Nature and probable Origin of the superficial Deposits in the Valleys and Deserts of Central Persia." Blanford, Esq., F.G.S.

By W. T.

In this paper the author described the general characters of the superficial deposits of Central Persia, and noticed the physical geography and rainfall of that country. He described especially the desert plains of the interior of the country, the paucity and scantiness of the streams, most of which terminate in salt swamps and lakes, and the occurrence of vast slopes of gravel on the margins of the desert plains, covering up the junction of the latter with the surrounding mountains. The desert plains he regarded as in general the beds of ancient lakes. His general results may be summed up as follows:-Persia has undergone a gradual change from a moister to a drier climate simultaneously with the elevation of portions of its surface, resulting first in the conversion of old river-valleys into enclosed basins containing large lakes, probably brackish or salt. Then, as the rainfall diminished, the lakes gradually dried up, leaving desert plains. The amount of subaerial disintegration among the rocks of the high ground he considered to be in excess of the force available for its removal, the water which now falls only sufficing to wash the loosened materials from the steeper slopes into the valleys; and hence the valleys in the upper parts are gradually being filled up with coarse gravel-like detritus, just as their lower portions have been already hidden beneath lake-deposits.

2. "On Caryophyllia Bredai, Milne-Edwards and Haime, from the Red Crag of Woodbridge." By Prof. P. Martin Duncan, M.B., F.R.S., V.P.G.S.

The author recorded the occurrence in the Red Crag of the Woodbridge district of a variety of Caryophyllia Bredai, M.-Edw. & Haime. The species was originally described from the Maestricht Chalk; and the specimen referred to, which was obtained by Mr. E. Charlesworth, appears to be a remanié fossil, derived from the uppermost beds of the Chalk, some traces of which still remain in the neighbourhood of Norwich.

3. "On the Cephalopoda-bed and the Oolite Sands of Dorset and part of Somerset." By James Buckman, Esq., F.L.S., F.G.S.

In this paper the author discussed the true position of certain beds containing abundant remains of Cephalopoda, found in various parts of the Jurassic region of this country, and of the sandy bed underlying the Inferior Oolite at Cleeve Hill and other places (called by Prof. Phillips the "Midford Sands"), which has been regarded by most authors as belonging to the Lias. From an investigation of the Cephalopoda-bed in quarries at Bradford Abbas in Dorsetshire, the author comes to the conclusion that it is quite distinct from the Cephalopoda-bed of Gloucestershire, and that it is the representative of the Rubbly Oolite at the top of Leckhampton