April 29, 1886] 



NA TURE 



621 



Thus, even if we imagine the general atmospheric current to 

 remain constant, a greater proportion of it would be thrown at 

 such times into those heated portions which had become good 

 conductors, but it is also probable that tha current itself would 

 be increased. Assuming the existence of currents at great alti- 

 tudes, the regularity and general characteristics of the diurnal 

 variations would seem to point to a direct magnetic action of the 

 currents rather than to any general induced change in the mag- 

 netic system of the earth, which, to produce the observed results, 

 would have to be of a very artificial character. The diurnal 

 variation of the declination, attaining a westeily maximum at 

 2 p.m. north of the equator, and an easterly maximum at the 

 same time south of it, would suggest the existence of currents 

 flowing northward and southward from the equator to the poles, 

 attaining a maximum in each hemisphere about two hours after 

 the sun had passed the meridian. To supply this flow we 

 should probably have to assume the existence of vertical cur- 

 rents ascending from the equatorial regions of the earth. At 

 this point Dr. Schuster has endeavoured to apply mathe- 

 matical analysis to the subject. From the recorded ob- 

 servations at Greenwich, Lisbon, Hobarton, St. Helena, 

 and the Cape, he has shown that the work done by a 

 magnetic pole describing a closed path in a horizontal plane at 

 those places is equal to the work done upon it, and consequently 

 no part of the ascending current can be inclosed by the path. 

 Hence the potential at those places obeys the law expressed by 

 the equation — 



d-V d-y , d-V 



-ZF^ + ^ + 1?? = °- 



From this Dr. Schuster has deduced two possible expressions 

 for the potential, one referring to a system of currents above our 

 heads, and the other to one beneath our feet. From the first of 

 these expressions it follows that for latitudes greater than 45° 

 the maximum of horizontal force should coincide with the 

 minimum of vertical force, and vice versa, and this is actually 

 the case at Greenwich ; while the opposite should hold if the in- 

 fluencing system were beneath us. For latitudes below 45° the 

 reverse of the above should be the case, and the observations at 

 Bombay, though less decided than those at Greenwich, would 

 seem to point the same way. On the whole, then, it must be 

 said that the results of the first attempt are very encouraging, 

 and point to the supposition that the greater part of the disturb- 

 ing cause lies outside the earth's surface. In a discussion that 

 followed, Mr. Whipple remarked that recent observations in 

 high latitudes seem to show that the aurora is not always at such 

 a great height as is usually supposed. Prof. A. W. Riicker 

 cited the well-known case when an observer saw what appeared 

 to be a meteor fall into the sun, while simultaneously, or nearly 

 so, there was recorded a magnetic disturbance on the earth, as 

 showing a direct solar action. Mr. Whipple, however, stated 

 that he had recently examined this point, and believes that the 

 very slight notch in the record, many similar to which have 

 occurred since, was of an accidental nature, and a mere coin- 

 cidence. Prof. McLeod suggested that the earth-current theory 

 might be tested by observations at the bottom of a mine, where, 

 according to the theory, the disturbances should be reversed. 

 Prof. Adams believed that there was nothing physically impos- 

 sible in the existence of such currents as the author imagined. — 

 On a relation between the critical temperatures of bodies, and 

 their thermal expansions as liquids, by Prof. A. W. Riicker, 

 F.R.S., and Prof. T, E. Thorpe, Ph.D., F.R.S. A paper by 

 the authors bearing the above title was published in the Joitrnal 

 of the Chemical Society of London for April 18S4. The sub- 

 stance of the paper was as follows. Prof. Mendeleeff has shown 

 that the expansion of liquids under constant pressure between 

 0° C. and their boiling-points may be expressed by means of 

 the veiy simple fornuila — 



V,= ' , 

 I - kt 



F, being the volume at t° C. (that at 0° C. being unity), and k 

 a quantity which differs for different substances, but whiqh may 

 for any one substance be considered invariable between 0° C. 

 and the neighbourhood of the boiling-point. From this law the 

 authors have obtained as a deduction the following expression for 

 the critical temperature (/"c) of any liquid — 

 TV, - 27 3 

 a{l^,- I)' 

 where Vi is the volume at /' C, 7' the absolute temperature, 



Tc = - 



and a a quantity which is very nearly constant for all substances, 

 and which was shown to be very nearly 2. — In a recent paper 

 (.-l/m. Cli. Ph , March 1886) MM. A. Bartoli and E. Stracciati 

 have discussed both of these formula:, and have applied them to 

 cases in a manner never intended by the authors. They have 

 expanded Mendeleeff 's formula into the series 



V!=l + kt + k'^t"- + k^'^ + . . . . 

 which is a geometrical progression, and they have objected to it 

 that the results of Pierre, Kopp, Hirn, Thorpe, &c., do not 

 give for the coefficients of/, t-, ('■', quantities in geometrical pro- 

 gression. The results of these observers are given in the usual 

 form — 



F, = I + at + i/' + cl^ + . . . . 



but, owing to unavoidable errors of experiment, the constants c, 

 d . . .of different observers differ very largely, and Mendeleeff 's 

 simple expression gives the results of all quite as accurately as the 

 facts will allow. MM. Bartoli and Stracciati have then criticised 

 the expression given by the authors, and have applied it to de- 

 termine the critical temperature of water from its expansion to 

 200°, whereas the original expression is only given as applicable 

 as far as the boiling-point. They have further recorded a 

 number of critical temperatures calculated by the formula to 

 tenths of a degree, for which the constant a would require to be 

 known to '025 per cent., whereas there is no reason for sup- 

 posing it known to within i per cent, or more. 



Zoological Society, April 6. — Prof. W. H. Flower, 

 F.R.S. , President, in the chair. — The Secretary exhibited, on 

 behalf of Mr. J. B. Martin, F.Z.S., a large tusk of the Indian 

 Elephant (Elephas itidkus), about 6 feet long and weighing over 

 100 lbs., stated to have belonged to a " rogue elephant," with 

 only one tusk, which had been killed at Goruckpore in 1S36. — 

 Mr. Sclater exhibited the heads and horns of two species of 

 Antelopes obtained in the vicinity of Lamoo, East Africa, be- 

 longing respectively to Strepsiceros iiniaidsanA Dainalis sairgal- 

 ensu. — Mr. F. E. Beddard read a paper on some points in the 

 anatomy of Chattiia chavaria. — Prof. Flower communicated a 

 paper, by Miss Agnes Crane, on a Brachiopod of the genus 

 Atretia, from Port Stephen, Australia, described in manuscript 

 by the late Dr. T. Davidson, and proposed to be i ailed Atretia 

 braderi. — Mr. J. G. Goodchild, H.M. Geological Survey, read 

 a paper on the disposition of the cubital coverts in birds. This 

 communication described the principal modes of imbrication of 

 the cubital coverts, as observed in healthy living birds of all the 

 leading carinate forms, and pointed out that there is a certain 

 correlation between particular styles of imbrication and various 

 other characteristics connected with the pterolysis, the myology, 

 the visceral anatomy, and osteology of the birds in question. 

 The paper concluded with some observations upon the origin of 

 the features described. — A communication was read from Dr. 

 Giinther, F.R.S., containing some further information on the 

 melanotic variety of the South African Leopard which he had 

 previously described. 



Geological Society, April 7.— Prof. J. W. Judd, F.R.S., 

 President, in the chair. — Edward George Aldridge, Charles 

 Brownridge, James Dennant, Charles Lane, Prof. H. Carrill 

 Lewis, and William Matthews were elected Fellows of the 

 Society. — The following communications were read : — On 

 glacial shell-beds in British Columbia, by G. W. Lamplugh. 

 Communicated by Clement Reid, F.G.S. This paper was 

 divided into two parts, relating respectively to Vancouver Island 

 and the Fraser Valley. Having to spend nearly a month at the 

 city of Victoria in 1884, the author had leisure for the investi- 

 gation of the geological features of the district, but he expressed 

 his regret that, at the time, he was unacquainted with the pub- 

 lications of Mr. Bauerman and Dr. Dawson on the subject. 

 The most important shell-beds were disclosed in an excavation 

 for a dry dock at Esquimault, V. I. Here a fissure in an igneous 

 rock had been filled in by glacial beds. Shells were most 

 numerous on the north side of the dock in Boulder-clay, asso- 

 ciated wdth irregular sandy seams, the whole being softer than 

 the general mass. The containing rock was not glaciated at 

 this point. Leda, Nucula, Cardium, Tellina, Mya, and Saxi- 

 cava are the principal genera. There was great difference in 

 the state of preservation according to position ; the shells below 

 the water-line being remarkably fresh, while acidulous waters 

 engendered by vegetable decay had attacked the upper portions. 

 The author concludes that the whole mass of drift, including 

 the shells, had been pushed up by ice in its passage southwards. 



