94 



NA rURE 



[May 26, 1904 



aluminium, tin, lead, cadmium, all chemically pure, and 

 also specimens of commercial copper and of steel pianoforte 

 wire. A dynamical method of experimenting was em- 

 ployed, the torsional oscillations of the wire under test 

 being timed by a method of coincidences capable of great 

 exactness. The method of coincidences is usually only 

 applied to the comparison of two nearly equal times, but 

 it is shown to be equally applicable to any two periods, even 

 if they are quite different. Observations were made, in 

 general, at five temperatures, viz. at the temperature of 

 the room, about 16° C, at 35° C, 55° C, 75° C. and 

 nio° C, and also in some cases at 126° C, the higher 

 temperatures being obtained by using the vapours of various 

 liquids boiling under atmospheric pressure. The co- 

 elficients of expansion of the wires used (which are required 

 in order to compare observations at different temperatures) 

 were determined by means of the measuring bench in the 

 physical laboratory of the University of Birmingham. 

 The internal viscosities of the wires, and the effect of in- 

 creased amplitude of vibration, were also investigated. The 

 main observations for the rigidity determinations were all 

 taken at an average amplitude of fourteen minutes. 

 The following is a summary of the principal results : — 

 (i) In all the materials examined, with the exception of 

 pure copper and of steel, the modulus of rigidity at one 

 temperature is not constant, but increases as time goes on. 



(2) The diminution of the modulus of rigidity per degree 

 rise of temperature between lo*' C. and 100° C. is constant 

 for pure copper and for steel, but not for any of the other 

 materials examined. 



(3) In general, the effect of heating to a high tempera- 

 ture is to increase the value of the rigidity modulus at 

 lower temperatures. 



(4) The internal viscosity of all the metals examined, with 

 the exceptions of soft iron and steel, increases with the 

 temperature. The internal viscosity of soft iron decreases 

 rapidly with rise of temperature, and reaches a minimum 

 value at about 100° C. There is a slight decrease also in 

 the case of steel. 



(5) Repeated heating and continued oscillation through 

 small amplitudes decrease the internal friction. 



(6) Both the internal friction and the period of torsional 

 vibration increase with the amplitude of oscillation. 



(7) Vibration through a large amplitude considerably 

 alters both the logarithmic decrement and period of 

 oscillation at smaller amplitudes. 



(8) The internal viscosity of a well annealed wire 

 suspended and left to itself gradually decreases. 



" On the Sparking Distance between Electrically Charged 

 Surfaces." By Ur. P. E. Shaw. 



Recent investigation fiqoi) on this subject has been made 

 by R. F. Earhart, who used voltages from 1000 to 38, the 

 corresponding distances being from 100 microns to \ micron. 

 In the present paper the voltages range from 150 to 

 3, and the distances of discharge from i micron to 

 1/500 micron. The instrument used to measure these 

 small distances is the electric micrometer, which works on 

 the principle of electric touch, and is therefore specially 

 suitable to measurements of this kind. 



The relation between voltage and sparking distance is 

 found to be linear, and direct from the origin ; hence it is 

 evident that there is no change in dielectric strength in 

 any film or films existing on the surfaces of the solid bodies 

 used at the points of discharge. Since i volt or there- 

 abouts is so frequently employed in electric circuits, there 

 is especial interest in knowing the sparking distance for 

 this voltage; it is about i/ioo micron, and unless sufficient 

 pressure is used to squeeze out dust or films until the metal 

 surfaces approach to this distance, no current can pass. 



The two surfaces used for discharge are a bead and a 

 plane, generally of polished iridio-platinum. The pressure 

 used is atmospheric. In working with such minute 

 distances care must be taken to exclude extraneous vibra- 

 tions, and the surfaces must be re-polished after every dis- 

 charge except when the voltages are less than 10. In 

 every case the discharge is observed by a telephone suitably 

 shunted. 



Geological Society, April 27. — Dr. J. E. Marr, F R.S., 

 president, in the chair. — On a new species of Eoscorpius 

 from the Upper Carboniferous rocks of Lancashire : 



NO. 1804, VOL. 70] 



VV. Baldwin and W. H. SutclilTe. The specimen described 

 was found in an ironstone-nodule occurring on a fairly 

 well marked horizon, about 135 feet above the Royley Mine 

 (or Arley Mine) coal-seam, at Sparth Bottoms, south-west 

 of Rochdale Town Hall. The nodules occur in a band of 

 blue shale, in which are well preserved remains of Carboni- 

 cola acuta, ferns, Calamaria, Prcsiwichia rotiindata, and 

 Bellinunts bellulus. The animal is well represented by both 

 the intaglio and relievo impressions ; these, however, only 

 show its dorsal aspect. The specimen is referred to a new 

 species. Dr. Peach is of opinion that the ancient species 

 visited the sea-shore in search of the eggs of invertebrates, 

 and the association of this new scorpion with king-crabs 

 at .Sparth Bottoms is in favour of this view. — The genesis 

 of the gold-deposits of Barkerville (British Columbia) and 

 the vicinity : A. J. R. Atkin. The gold-bearing area of 

 Cariboo is roughly confined, within a radius of 20 miles 

 of Barkerville, to the band of crystalline rocks known as 

 the Cariboo schists, generally assigned to the Lower 

 PaliEozoic group. The veins follow the strike but not the 

 dip of the rocks ; the gangue is similar to that associated 

 with the nuggets in the placers. While all the reefs carry 

 gold, none have been found rich enough to account for the 

 placer-gold. The placer-gold has probably been derived 

 from the enriched outcrops of the veins which once existed 

 above water-levpl. Such enrichment is due to the leaching 

 out of pMiir^ lr;i\int;- the Icss soluble gold in lighter quartz, 

 and to ai tual rmii hnient by precipitation. While the en- 

 riched zone was bfing formed, the weathering of the surface 

 kept removing the leached outcrop, and constantly exposing 

 fresh surfaces to atmospheric influences. To the weather- 

 ing of these outcrops the rich placers are attributed. The 

 denudation of the reefs and the deposition of gold in the 

 gravels appear to have taken place in Tertiary times. 



Zoological Society, May 3.— Mr. G. A. Bnulenter, F.R.S., 

 vice-president, in the chair. — Mr. Oldfield Thomas, F.R.S., 

 read a paper on the osteology and systematic position of 

 the rare Malagasy bat Myzopoda aiirita. — Mr. F. E. 

 Beddard, F.R.S., read a third of a series of papers on the 

 anatomy of the Lacertilia, which dealt with points in the 

 vascular system of cham;i.'leon and other lizards. — .\ com- 

 munication was read from Mr. A. D. Imms containing 

 notes on the gill-ral<ers of the ganoid fish Polyodon. — Dr. 

 \V. G. Ridcwood read a paper on the cranial osteology of 

 the fishes of the families Elopids and Albulida.", with re- 

 marks on the morphology of the skull in the lower teleostean 

 fishes generally. 



Entomological Society, May 4. — Irof. E. B. P.niltnn. 

 F.R.S., president, in the chair. — Mr. W. J. Kaye exhibited 

 a piece of the plant Eupalorium macrophyllum from 

 British Guiana, attractive to Lycorea, Melina-a and 

 Mechanitis species of that region, and a remarkable larva- 

 like twig of birch.' The resemblance was so complete that 

 even the head, the segments, the appressed legs and the 

 anal claspers appeared to be represented. It had been found 

 on Oxshott Heath while searching for larva? of Gcomctra 

 papUionaria. He also exhibited on behalf of Mr. C. P. 

 Pickett a pupa of Ritmia cratacgata which had spun up 

 in an empty pupa case of Picris brassicae. The latter was 

 on the roof of a breeding-cage, and the geometrid larva 

 had completely crept inside to spin its cocoon. — Mr. J. E. 

 Collin exhibited Corctlira obscuripcs, v. d. Wolf 

 (? = C. fusca, Staeg.), a little known species of the genus, 

 and new to the British list, which he had found in some 

 numbers at Newmarket. — Mr. G. T. Porritt exhibited a 

 living larva of Agrotis ashworthii, of which species he had 

 found considerable numbers on one of the mountains of 

 Carnarvonshire during the last week in April. — Commander 

 J. J. Walker, R.N., exhibited a gall sent him by Mr. Harold 

 S. Mort, identified by Mr. Froggart as Brachyculis duplex, 

 Schrader, and found at Wentworth Falls, Blue Mountains, 

 N.S.W., where it was by no means common.-— Mr. G. H. 

 Verrall exhibited three specimens from the Hope collection 

 at Oxford of ycoitaintts cothuniatus, Meig., an .Asilid not 

 previously recorded as British. Thev were taken near 

 Oxford by Mr. W. Holland. He a'iso stated that the 

 Anthrax exhibited at the last meeting on behalf of Mr. 

 R. G. Bradley was .1. circumdala, Meig., a species recorded 

 before, but not observed for more than fifty years past. — 



