equally incompetent to bring about the desiderated climatic conditions, and that even a former much greater elevation of the land, combined with the appearance of a Sahara sea, would fail to supply us with the severe winter climate that was necessary to produce the great agglomerates. They thought that the most probable explanation of the phenomena described is that the cold conditions referred to were contemporaneous with that general refrigeration of climate which took place over so vast an area in our hemisphere during Pleistocene times. The limestone-agglomerates they look. upon as the equivalents of those glacial deposits that occur so plentifully in our own and other countries; and the bone-breccias, which are intermediate in date between the lower and upper limestone agglomerates, are paralleled by the interglacial beds of the British Islands, Sweden, Switzerland, &c.

2. "Notes on the Geology of Japan." By J. G. H. Godfrey, Esq., F.G.S.

The author stated that Yesso, the most northern island of the Japanese group, had been geologically surveyed under the direction of Mr. Lyman, but that the geology of the other islands was chiefly known from Richthofen's general description. He finds that the classification of formations proposed by Lyman for Yesso holds good in all the other islands. Thus, going from newer to older deposits, he distinguishes :-

1. New alluvium, formed by existing rivers.

2. Old alluvium, formed by ancient rivers.

3. New volcanic rocks, consisting of basalt and rhyolite. Most of the Japanese volcanoes are extinct; but a few, such as Asamoyama, are in the solfatara stage; hot springs abound, and earthquakes are frequent.

4. Toshibetsu group, Middle or Lower Tertiary sandstones, clays, and conglomerates, containing lignite and petroleum.

5. Old volcanic series, rhyolitic rocks, often distinctly bedded, covering a vast area, and with numerous lodes and deposits containing gold, silver, copper, lead, and blende.

6. Horimui group, a coal- and lignite-bearing series of considerable extent, apparently best developed in the western part of Japan, and especially in the north of the island of Kiushiu, where the deposits are shown by fossil evidence to be of Cretaceous age.

7. Kamoikotan or metamorphic group, consisting of various schistose and gneissic rocks, distinctly stratified, and usually showing a dip of upwards of 60°. Owing to the absence of fossils the age of this group is still undecided; Richthofen regards it as Silurian or Devonian. Granite and diorite are frequently intruded into this series; and they contain some important mineral veins.

The author went into considerable details upon the useful minerals of Japan, noticing their mode of occurrence and the quantities in which they are produced. The most important of them are:coal and lignite, copper, silver, gold, iron, petroleum, lead, and tin; those of less consequence are sulphur (from the old craters), antimony, mercury, kaolin, and salt.

LXVI. Intelligence and Miscellaneous Articles.

CONTRIBUTION TO THE THEORY OF THE MOTION OF ELECTRICITY IN SUBMARINE AND UNDERGROUND TELEGRAPH-WIRES. BY G. KIRCHHOFF.

ASSUMING that the induction-effects produced by alterations of

дф
дх

&c., where A de

the current-intensity may be neglected against the influence of the charges of an underground telegraph-wire, Sir W. Thomson has referred the propagation of the electricity therein to the same laws as the conduction of heat. G. Kirchhoff develops this relation in connexion with the equations developed by Helmholtz respecting the components of the current-density (u=—λ. notes the conductivity) and of the electrostatic moment dependent on the dielectric polarizability* (a=−k; &c.), if 4 denotes the electrostatic potential, which is a function of x, y, z and consists of three parts, arising:-first, from the free electricity in and upon the conductor; secondly, from dielectric polarization; and, finally, from the double electric layer at the boundary surfaces of heterogeneous conductors. From the calculations, which cannot be given in abstract, it follows that

дф

da

•=eßz (C'cos (nt+az) +C' sin (nt+az))+e-ßz (D cos (nt—az)

+D' sin (nt - az)),

which equation represents two passages of waves in opposite directions along the z axis of the wire, in which the height of each wave as it moves forward diminishes correspondently to the value ẞ. The

27

n

period for according to the time is ẞ and a are given by the equations

21

where Pi and P2 are the internal and external radius of the guttaperch sheath, A and A, the conductivities of it and the wire, 4μ=1+4k the constant of dielectricity of the gutta-percha.

Therefore the velocity of propagation of the waves increases with the conductivity of the gutta-percha, simultaneously with which their height diminishes as they travel onwards.

If the conductivity of the gutta-percha λ=0, then becomes

If the wire is infinitely long, then (if, for z=0, 4= cos nt) is

4=e-Bz cos (nt-az).

Further, the following case is discussed:-that the wire possesses the length 7, but has its termination connected with one of the coatings of a condenser, the other side of which is led away to earth. For the calculation in question, as well as the rest of the working, which cannot well be given in abstract, we must refer the reader to the original memoir.-Beiblätter zu den Annalen der Physik und Chemie, 1878, No. 1, vol. ii. pp. 221–223.

EXPERIMENT FOR ILLUSTRATING THE TERRESTRIAL ELECTRICAL CURRENTS. BY PROFESSOR WM. LEROY BROUN.

The following experiment enables a lecturer to exhibit to a large audience, in a very simple way, the action of the currents of electricity that pass around the earth. The experiment was suggested on reading an article by Professor J. W. Mallet, in the Philosophical Magazine for November 1877.

A rectangular frame was made of light poplar wood, of section three by two centimetres, whose sides were in length a fraction over a metre, and in breadth three fourths of a metre. About the perimetre of this rectangular frame were wrapped twenty coils of insulated copper wire; each extremity of the wire was made to terminate near the centre of one of the shorter sides, and passing through the wooden frame was fastened and cut off about three centimetres from the frame. This rectangular frame was then so suspended, in a horizontal position, by wires attached to the frame of an ordinary hydrostatic balance, that the longer sides were at right angles with the beam. By adjusting weights in the pans the index of the balance was brought to the zero-point. Two small orifices bored in a block of wood, a centimetre apart, served as mercury-cups, in which the extremities of the short terminal wires were immersed. Near the bottom and through the walls of these wooden cups were screwed small brass hooks, which served as connexions, to which the wires of the battery were attached. The balance was now so placed that the longer sides of the suspended rectangle were at right angles with the magnetic meridian or in the magnetic east-and-west line.

When the current from the battery was made to pass around the rectangle from east to west on the northern side, and from west to east on the southern side, by the theory of terrestrial magnetism the northern side of the rectangle would be attracted and the southern side repelled; and that this was so, the corresponding deflection of the balance rendered plainly visible. When the current was reversed the deflection was in the opposite direction. By breaking and closing the circuit at proper intervals to augment the oscillations, the large frame was readily made to oscillate through an arc of five degrees. When the sides of the rectangle were placed north-east and south-west the current produced no sensible

effect. A bichromate-of-potash battery of sixteen cells, with plates of zinc and carbon twenty-five by six centimetres, was used.

With a rectangle containing a larger number of coils of wire, attached to a very delicate balance, by using a constantly acting battery, the variation in the magnetism of the earth might thus be advantageously observed.-Silliman's American Journal, May 1878.

ON THE DIFFUSION OF CARBONIC ACID THROUGH WATER AND ALCOHOL. BY PROF. STEFAN.

When carbonic acid is parted from the atmospheric air by a liquid cylinder, it diffuses through the liquid into the external space. If the carbonic acid be kept under constant pressure, the rate of diffusion will be constant; the amount of carbonic acid issuing in the unit of time will be to the cross section of the cylinder directly, to its length inversely proportional.

The density of the carbonic acid diminishes from the inner to the outer boundary layer of the liquid which is saturated with the acid. The quantity of carbonic acid passing in the unit of time through the unit of the cross section is proportional to the fall in the density. The proportionality factor is the coefficient of diffusion, and can be determined from such observations.

A second method for determining it consists in the observation of the penetration of carbonic acid into a cylinder of liquid of great length. The amount of gas which has entered into the liquid from the commencement of the experiment up to a certain time is proportional to the square root of this time.

The velocities with which gases spread in liquids are of the same order as those with which salts diffuse in their solvents. The coefficient of diffusion of carbonic acid in water is nearly as great as that of potassium chloride. The coefficient for the diffusion of carbonic acid in alcohol is twice as great.

Oxygen and nitrogen diffuse in both liquids more quickly than carbonic acid; but the highest velocity of diffusion belongs to hydrogen gas. The peculiarities by which the gases are characterized in reference to their molecular motion in the free state, and which come out especially in their diffusion through porous solids, they still possess in the interior of liquids by which they have been

absorbed.

That reciprocal action between gases and liquids, in consequence of which different gases are absorbed in different measure by one and the same liquid, has no influence upon the velocity of the diffusion-motion; the greater or less capacity of absorption of the gas determines in each given case the density of the diffusioncurrent only. Kaiserliche Akademie der Wissenschaften in Wien, mathematisch-naturwissenschaftliche Classe, March 21, 1878.

477

INDEX TO VOL. V.