the upheaval of Australia and New Zealand was approximately synchronous with that of the great mountain-chains of the Old World, with the closure of the Panama area, and the depression of the areas on either side of the American continent.

2. "Note on a new and undescribed Wealden Vertebra." By J. W. Hulke, F.R.S., F.G.S.

The author in this note describes a very large Wealden vertebra which he obtained last autumn at Brook, Isle of Wight, remarkable for its great size, its extremely light structure, and the extraordinary development of the processes connected with the neural arch. It consists of a thin outer shell, enclosing a very open cancellated tissue, having extremely large spaces, comparable with those of Pterosauria, and surpassing those of the cancellous tissue in any of the known larger Dinosaurs. A wedge and notch, similar in principle to the ophidian zygosphene and zygantrum, but differently placed, are superadded to the ordinary articular processes. A broad horizontal platform stretches along the side of the arch from the transverse process to the postzygapophysis. The neural spine is composite; all the outstanding parts are supported and strengthened by thin bony plates. Only a small part of the centrum is preserved, so that the form of this, and in particular of its articular faces, is not determinable. The author notices, in conclusion, certain textural resemblances between the vertebra and a peculiar Streptospondylian vertebra in the British Museum, from the Weald of the south-east of England.

3. "Note on the Middle Lias in the North-east of Ireland." By Ralph Tate, Esq., A.L.S., F.G.S.

The author remarked that hitherto no higher member of the Jurassic series than the Lower Lias has been detected in Ireland. He stated that he had received from near Ballintoy some blocks of a grey, marly, micaceous sandstone, containing an assemblage of fossil forms, indicating that the rock from which they were derived belonged to the lowest part of the Middle Lias. The origin of these specimens, which were obtained "from cultivated fields and patches of drift," was said to be still unknown; and the occurrence of Hippopodium ponderosum, associated with Middle-Lias species, as in the Island of Skye, coupled with the agreement in lithological composition between the Irish blocks and the Pabba shales, led him to suggest the possibility that the former may have been transported from the Hebrides by glacial action.

February 23rd, 1870.—Joseph Prestwich, Esq., F.R.S.,
President, in the Chair.

The following communications were read :—

1. "Additional observations on the Neocomian Strata in Yorkshire and Lincolnshire, with notes on their Relations to the Beds of the same age throughout Northern Europe." By J. W. Judd, Esq., F.G.S.

This

paper embodied the results of the author's further study of

the Neocomian beds of the north of England, in connexion with those of North-western Germany.

The inland development of these strata in the Vale of Pickering was described as being greatly obscured by superficial deposits. The beds, however, exposed at Reighton, West Heslerton, and Knapton were shown to agree, both in physical and palæontological characters, with several of those before described in the cliff section at Speeton. The Neocomian ironstones of Lincolnshire have, since the date of the former paper on the subject (1867), been extensively opened out by mining-operations; and the valuable and instructive sections thus afforded were described in detail. A general sketch was then given of the range and characteristics of the Neocomian strata in Yorkshire and Lincolnshire.

Evidence was next adduced to show that strata of the same age, and remarkably similar in character, had been deposited over a very wide area in Northern Europe. Throughout the whole of these districts, however, the Neocomian strata were very inadequately exposed, and afforded no good general sections; and the Speeton Cliff thus acquired an additional interest from the fact that it forms a valuable, and almost the only, key whereby we can correlate the beds over this vast area.

i.

Studying the continental deposits in this manner, by the aid of the Speeton section the fossiliferous clays of the island of Heligoland were shown to belong to the "zone of Ammonites Speetonensis," e. the upper part of the Lower Neocomian. The boulders found in the drift deposits of Holland were referred to as evidence of the former wide extension of limestones similar to those of Tealby in Lincolnshire. In Westphalia the sandstones, limestones, ironstones, and clays, so extensively developed in the hills of Bentheim and the Teutoburger Wald, were shown to be of Middle Neocomian age, while certain beds of clay in the same district were referable to the Upper Neocomian. In Hanover the "Hilsthon" of M. Fr. Ad. Römer was shown to be in its upper part Upper Neocomian, and in its lower part Middle Neocomian, the latter passing locally into beds of oolitic ironstone, sandstones, and limestones precisely similar to those of the same age in Lincolnshire. The narrow strip of highly inclined Neocomian strata along the northern foot of the Hartz was shown to belong to the same two subdivisions. In Brunswick, however, the Neocomian series was more complete; for underneath some 400 feet of clays, which on paleontological evidence clearly belong to the Upper and Middle divisions, there were certain marly limestones, in places becoming ferruginous, containing an abundant and interesting fauna which was most unmistakably that of the Lower Neocomian.

It was then pointed out that in northern Germany there was evidence, as in this country, of an unconformity existing between the Upper Cretaceous and the Neocomian, as well as between this last and the Jurassic. Attention was also drawn to the fact that while the Neocomian series was complete in Yorkshire and Brunswick, its lowest member was absent in the intermediate districts, being

apparently replaced by the freshwater deposits of the German Wealden.

2. "On Deep-mining with relation to the Physical Structure and Mineral-bearing Strata of the S. W. of Ireland." By Samuel Hyde, Esq. Communicated by R. Etheridge, Esq., F.G.S.

XVIII. Intelligence and Miscellaneous Articles.

ON THE USE OF THE ELECTRIC CURRENT IN CALORIMETRY. BY M. J. JAMIN.

JOULE'S law gives the heat which is developed in conductors

when traversed by currents. A metal wire may be regarded as a focus. It may have any possible form and be placed where we please, in the midst of liquids or gases; a quantity of heat will be given off proportional to the time, to its resistance, and to the square of the intensity of the current; it will heat those bodies by a quantity which can be measured, and which is inversely proportional to their mass and to their specific heat. Hence results a new process to determine this specific heat. After numerons trials I fixed upon the following arrangements.

I. Case of Solids and of Liquids.-In dealing with a solid or a liquid, I use as a calorimeter an elongated cylindrical vessel of thin copper, on which is coiled 8 metres of German-silver wire 0·2 millim, in diameter, and covered with silk. This spiral commences at the bottom of the vessel, and ascends to one-third of its height; it is connected with the circuit by thick copper wires; its resistance is measured for all the temperatures of the experiment. I envelope it with a thin silk ribbon to keep it in its place, some swan's down to insulate it, and I enclose the whole in an envelope of thin copper polished. When the calorimeter contains a liquid and a current is caused to pass through the spiral, nearly all the heat will be transmitted to the sides, then to the liquid; a scarcely appreciable portion will be transmitted to the swan's down.

With this view, fresh liquid must be continually brought into contact with the sides by uniform agitation. For this purpose a basket of metal gauze, formed of two concentric tubes, is immersed in the calorimeter. A small machine raises and lowers it at equal intervals; a thermometer marking the hundredth of a degree is immersed in the central tube; it is fixed, and is read with a telescope. When the specific heat of solids is to be measured, they are placed in the basket in the water.

This constitutes the entire apparatus; the operation is one of extreme simplicity. After pouring into the calorimeter the weight of liquid which is to be investigated and agitating it some time, the variation (if any) of the thermometer is observed for five minutes. Generally it does not vary. A current of a measured intensity is then made to pass during one, two, &c. minutes, until an elevation

of 3 or 4 degrees is produced; this is noted, after which the cooling of the thermometer is observed during five minutes. The quantity of heat given off is known, the effect it has produced is calculated, and from the known formulæ of calorimetry the desired capacity is deduced*.

The old method required two operations, which were :-the first, to heat in a stove for a long time the body to be studied, and to pour it with minute precautions into the calorimeter; the second, to observe the thermometer immersed in the calorimeter. In the method which I propose the first operation is omitted, and the second suffices such as it was before. The corrections remain the same, but are

simplified.

They are simplified because a lower temperature is sufficient, and because, the heat given off being proportional to the time, the method known as Rumford's is applicable. We may even dispense with all correction, as I shall show.

I provided the external envelope of the apparatus with a spiral twenty times as long as the first, and immersed the whole into a vessel containing twenty times as much liquid as the calorimeter, and forming a medium in which the latter is immersed. The current passes simultaneously into the two spirals; it produces there heats proportional to the quantities of liquid, and consequently equal heatings. At each moment the temperatures of the calorimeter and its surroundings are in equilibrium, and the first, neither gaining nor losing any thing by radiation, is subject only to the action of the current. It is impossible to maintain this equilibrium strictly during the whole time of the experiments if they are prolonged; but it is very easy to establish it within a few tenths; and that is sufficient to obviate all necessity for correction. Thus we can measure for each degree the specific heat of a liquid (water or alcohol for example) from the lowest temperatures to its boiling-point.

I have verified this method by determining the capacities of iron and of copper, which are the most difficult to obtain exactly, because they are very small. I found 0.098, 0.093. M. Regnault obtained

the numbers 0 113, 0.095, which are a little larger; but he operated with a higher temperature.

II. Of Gases and Vapours.-The advantages of this method are especially apparent when treating of aëriform fluids. A gaseous current passes through a glass tube to the middle of a cork of badly conducting material; a thermometer there measures its temperaIt immediately enters a second tube through the folds of a metal spiral or a bundle of twisted wires traversed by electricitythat is to say, through a focus; it becomes heated and meets a second thermometer, which measures its increase of temperature. Before

ture.

* Suppose two experiments to be made with the same current during the same time, with the weights P and P' of water and of the liquid to be studied. The quantities of heat are the same; they have heated the liquids and ' degrees. Denoting the weight of the calorimeter reduced to water by π, and the capacity sought by x, we have

(P+π)0=(P'x+ñ)0'.

emerging, the gas is led round the first tube to prevent any loss by radiation and conductibility; and when the temperature has become stationary, we may say that all the heat of the focus, which is known, is taken by the gas, the temperature of which is increased by a measured quantity; hence the specific heat can be deduced.

There are two advantages in this method. The first is, that the greatest cause of error which Delaroche and Bérard, and afterwards M. Regnault, met with is suppressed. In their experiments the gas reached 100° in a calorimeter at 10°; and the greatest difficulty was felt in appreciating the heat which passes by conductibility from the hot tube to the cold calorimeter. In my method the gas reaches at the ordinary temperature (say, 10°), it passes from the spiral at about 20°: the difference is 10°; it was 90° before; the present error is at most one-ninth of the former.

Here is the second improvement. The whole of my apparatus is the size of a finger, it is of thin glass; it might be of mica, even of goldbeater's skin; it weighs no more than a litre of gas, and expends no more heat in reaching the final temperature. Ten litres of gas are sufficient to make one measurement; thus the difficulties which for a long time had to be overcome in order to obtain a uniform current disappear, ordinary gasometers suffice, and the method is applicable even to vapours. A first determination gave the number 0-242 for air, instead of 0.237, which M. Regnault found.

Thermometers, even, may be dispensed with, and the temperature measured by the increase of resistance in the wires. It is known that a resistance r at zero becomes r(1+at) at t degrees. That being the case, let two equal bundles of wires be placed one after the other in a tube; then, having decomposed the total circuit into two equal derived circuits, let us make each of them pass, first through one of the two bundles of wires, then into a differential galvanometer; the latter remains at zero. But if a current of gas at t degrees be sent through this tube, it will pass at t+0 in the first spiral, at t+20 in the second; they take a difference of temperature 0, a different resistance, and the galvanometer is deflected. It is reduced to zero on introducing, by means of a special rheostat, a platinum wire into one of the circuits. The length of this wire is proportional to the increase of temperature ; it admits of measurement.

The same apparatus is applicable to vapours. The liquid to be examined is distilled as regularly as possible; the current of vapour is at first superheated by the first bundle of wires, it afterwards traverses the second, becomes heated by a quantity 0, which is measured as before; the vapour is condensed, and afterwards weighed. In order to take into account the irregularities of the distillation, it is necessary to observe the apparatus from minute to minute.

III. Latent Heat.-In order to measure latent heats, a double alembic is employed, of which one part is exterior; the liquid in it is caused to boil, and the vapour is brought there after having been condensed by a refrigerator: the effect of this is simply to raise to the boiling temperature the interior alembic, which contains the same liquid, and in which is immersed the spiral, the resistance