458 



NATURE 



[March 8, 1900 



were made with a Callendar compensated constant pressure 

 hydrogen thermometer. The correction for the contraction of 

 the glass bulb was determined by measuring directly the linear 

 expansion of glass between - 190° C. and 20° C. This was 

 found to be '0000073, Regnault's measurement between 0° and 

 10° being 0000085. The values for the boiling points of oxygen 

 and nitrogen agree fairly well with those given by Olszewski and 

 Estreichcr. Boiling nitrogen has a great tendency to super- 

 heat. This can be obviated by passing a rapid current through 

 the boiling liquid, or by dropping in pieces of copper. There 

 does not appear to be any connection between the ratio of the 

 vapour-pressures and the composition ot the gaseous phase in 

 the distillation of oxygen and nitrogen at constant pressure. It 

 is proposed to investigate the distillation at constant temperature. 

 Prof. Ramsay drew attention to the uses of liquid air for 

 carrying on researches at low temperatures. It is non-explosive, 

 easy to work with, and is easily kept either by means of a 

 vacuum jacket or by surrounding it with cotton-wool. Prof. 

 Callendar referred to the question of superheating, and stated 

 that the constant pressure thermometer was more accurate than 

 the constant volume one for measuring low temperatures. — A 

 paper on the reversibility of galvanic cells, by Mr. T. S. Moore, 

 was read by Dr. Lehfeldt. In these experiments the reversi- 

 bility of cells, such as the Daniell and the Clark, which are 

 assumed to be reversible, was tested by allowing the cell to send 

 a current, and by sending a current through the cell. The 

 E.M.F.'s of the cells were determined by means of a Crompton 

 potentiometer, and from the E.M.F.'s on open and closed cir- 

 cuits the internal resistances of the cells were calculated. Prof. 

 S. P. Thompson asked if experiments had been made upon 

 Leclanche cells where the products of the action escape. Dr. 

 Lehfeldt said that experiments were not made upon these cells 

 because they were known not to be reversible. ^A paper on the 

 damping of galvanometer needles, by Mr. M. Solomon, was 

 postponed until the next meeting. 



Zoological Society, February 20.— Dr. Henry Wood- 

 ward, F.R.S., Vice-President, in the chair. — Mr. Oldfield Thomas 

 exhibited a specimen of a kangaroo from Northern Australia 

 allied to Macropus eugenii, but distinguished by its pale colour and 

 long soft fur. It was proposed to name the species M. bed/ordi, 

 after the Society's President, who had given the specimen to the 

 British Museum. — -Mr. Thomas also exhibited a kangaroo from 

 Western Australia, apparently referable to Macropus robushts, 

 but separable sub-specifically by its nearly uniform rufous fawn- 

 colour. It was named Alacroptis robustus cet-vimis. — Mr. R. 

 Lydekker exhibited, on behalf of Mr. Rowland Ward, the 

 horns and skins of a male and female, in the winter coat, of the 

 sheep which, on the evidence of specimens in the summer dress, 

 he had recently named Ovis sairensis. — Mr. Lydekker also ex- 

 hibited, on behalf of Mr. Rowland Ward, the skull, horns, and 

 skin of a remarkable ibex obtained in the Altai, which he was 

 inclined to refer provisionally to Capra sibirica dauvergnei. — 

 Mr. C. W. Andrews gave a brief account of the land fauna and 

 the general physical features of Christmas Island, accompanied 

 by some lantern illustrations. He then read a p iper on the 

 marine fauna of that island, and pointed out that, the conditions 

 being unfavourable, no systematic attempt to collect marine 

 animals had been made, but that, nevertheless, a certain number 

 of specimens had been obtained, which were enumerated and 

 described in this paper by various specialists. Mr. E. A. Smith 

 had determined twenty-seven species of MoUusca, all common 

 Indo-Pacific forms. Of the corals Mr. H. M. Bernard had des- 

 cribed about twenty-two species, referable to fifteen genera, two 

 of them, viz. Goniastraea aurictilaris and Montiporo spongilla, 

 being new. The sponges had been determined by Mr. R. Kirk- 

 patrick, and were referred to thirty-one species and twenty-four 

 genera, of which six new species sand two new varieties were 

 described. From sand dredged from a depth of eleven fathoms 

 Mr. F. C. Chapman had determined twenty-four species of 

 Foraminifera. — Mr. R. Lydekker communicated a paper by Dr. 

 Einar Lonnberg, of Upsala, containing the results of the dis- 

 section of the soft parts of several specimens of the musk-ox 

 (Ovibos moschatus), obtained in Greenland during the recent 

 Swedish Expedition under the direction of Prof. Nathorst. The 

 result of his observations was to indicate that this animal could 

 not be regarded as a member of the Caprine group, while it was 

 equally widely separated from the Bovifiae. In the absence of a 

 knowledge of the soft parts of the Takin {Btidorcas), the author 

 was unable to accept the suggested affinity of the musk-ox with 

 that animal. Consequently, for the present at least, it might be 



NO. 1584, VOL. 61] 



regarded as representing a subfamily by itself. — Mr. F. E. Bed- 

 dard read a paper on the anatomy of an earthworm, Ben- 

 haniia caecifera, a specimen of which he had lately had sent to 

 him from Ashanti. This species had been described by Dr. 

 Benham in 1895, chiefly from external characters, no detailed 

 account of its internal structure having been given. —A paper 

 was read by Mr. < Oldfield Thomas on the mammals obtained 

 by Mr. H. J. Mackinder during his recent expedition to Mount 

 Kenya, British East Africa. Fourteen species from the mountain 

 were enumerated, besides five others specimens of which had 

 been obtained at Niarobi. Three species of Dassy {Procavia) 

 were described : one (P. jacksoni) from the Eldoma Ravine, like 

 P. abyssinica, but with coarser fur and more prominent dorsal 

 spot; a second {P. mackinderi) from the alpine zone high up 

 on Mount Kenya, like P. jacksoni, but larger and with much 

 longer fur ; and a third {P. crawshayi) from the forests at the 

 foot of Mount Kenya, allied to P. valida, but more rufous and 

 with a whitish dorsal spot. 



Linnean Society, February 15.— Mr. C. B. Clarke, F.R.S., 

 Vice-President, in the chair.— Mr. R. Morton Middleton, 

 exhibited a series of specimens of Aspleninm Bradleyi, 

 Eaton, one of the rarer rock ferns from Tennessee, to show its 

 extreme variability. The simplest fronds exhibited were found in 

 a damp, cold, perpendicular rift, which no sunshine could enter, 

 at an elevation of about 1700 feet ; these fronds had the simple 

 pinnate structure, with green rhachis and rounded, toothed 

 pinnae of A. viride, Hudson, but were more coriaceous than in 

 that species. Dr. Gattinger, author of the " Tennessee Flora," 

 was satisfied that the plant was A. viride ; and General Kirby 

 Smith, who had had ample opportunity of studying A. Bradleyi 

 on the eastern slopes of the Cumberland Plateau, remarked that s 

 A. viride and A. Bradleyi were so much alike that they might \ 

 be varieties. The other plants exhibited, however, showed a ' 

 gradual tendency to become more and more compound, culmin- ^ 

 ating in a luxuriant specimen with pinnatifid fronds 10 inches | 

 long, the green rhachis becoming purple and shining in all the , 

 plants exposed to the sun's rays.— Mr. J. C Shenstone exhibited 4 

 a collection of 700 photographs of British flowering plants, to i 

 show what could be accomplished by means of the camera in the ^ 

 direction of botanical illustration. He contended that photo- 4 

 graphy was the only means by which the lines and masses of J 

 our flowering plants, as truly characteristic as the less subtle , 

 characters by means of which botanists group and arrange plants . 

 into orders, genera and species, could be readily reproduced, i 

 He explained the various technical processes and apparatus .: 

 necessary for successful plant photography, and alluded to the "< 

 difficulties inseparable from the photography of plants in their i 

 natural habits, &c. His remarks were illustrated by means of ' 

 lantern-slides. — The Zoological Secretary gave an account of a I 

 paper by Dr. R. F. Scharff, Keeper of the Natural History Col- ' 

 lections in the Science and Art Museum, Dublin, describing a ^ 

 Land Planarian discovered by the author in the Pyrenees during \ 

 the autumn of 1899, which he had named Rhynchodesmtis 1 

 Howesi. The paper contains a description of the leading facts \ 

 of structure of the worm, which is a colossal representative of \ 

 the genus to which it belongs, since it measures 130 millim. in ' 

 length — i.e. twice that of the largest species of the genus hitherto ' 

 known. It was found at Eaux Chaudes, 2000 feet above sca- '\ 

 level, coiled round the shell of a Helix tiemoralis, which it had ij 

 overcome and was about to devour. —Mr. J. B. Carruthers ex- ^ 

 hibited specimens and lantern-slides to illustrate the growth of l 

 the vegetable canker Nectria ditissima on the cocoa-plant, and , 

 gave an account of certain experiments which he had made to j 

 destroy it without injury to the tree which it attacked. j 



Cambridge. \ 



Philosophical Society, February 5. — Mr. Larmor, ; 



President, in the chair. — lonisation of gases in an electric \ 



field. Prof. J. J. Thomson. The view put forward in this \ 



paper is that the ionisation of a gas in an electric field is brought j 



about by the presence of ions already in the field. These ions ; 



move under the electric force and acquire energy which can be ,j 



spent in ionising the gas. It is shown that this view would y'j 



explain why an electric field of definite strength is required to i 



produce discharge, why a thin layer of gas is electrically j 



stronger than a thick one, why the electric strength diminishes ,j 



with the pressure of the gas until a critical pressure is reached j 



when the strength is a minimum, as well as many phenomena ' 

 connected with the discharge through gases at low pressure. -|f5 

 On differenlial equations with two independent variables. Dr. 



