262 



NATURE 



[July io, 1890 



easily be shown by tapping an ordinary " philosophical ham- 

 mer"; separation of the column always leaves a bubble which 

 can then be floated off. He had also found that, in freeing 

 liquids from air by boiling, it was advantageous to have a long 

 escape tube so that part of the liquid condenses and runs back. 

 — Mr. C. V. Boys read a paper on the measurement of electro- 

 magnetic radiation by himself, Messrs. A. E. Briscoe and W. 

 Watson. When Mr. Gregory described his new electric radia- 

 tion meter on November i, 1889, one of the authors said that 

 the observed effect might be due to some cause other than ex- 

 pansion by heating, and that if it was a true heating effect it 

 might be measured thermally. The present communication 

 describes experiments undertaken to investigate the question. 

 The first method employed was developed from the idea that if 

 two fine wires be placed near together, and both act as resonators 

 to a primary oscillator, the electrodynamlc attraction caused by 

 the electric currents up and down the wires, and the electrostatic 

 repulsion between the charges on them, might result in the rela- 

 tive motion of the two wires. From theoretical considerations 

 based on the assumption that the currents are harmonic in lime 

 and space, the authors inferred that the electrodynamlc effect would 

 preponderate at the middle of the wires, whilst the electrostatic re- 

 pulsion would be greatest at the ends. To cause the attractions and 

 repulsions to conspire in producing rotation, cranked 

 resonators, A, B, c (see figure), were made; one was ' 1-^ 



fixed, and the other suspended by a quartz fibre, to 

 turn about a middle line, DE. These were inclosed 

 in a glass vessel, and on starting the oscillator a turn- , 

 ing movement was observed in a direction opposite ^^ 

 to that expected. This motion was eventually traced 

 to the electrostatic influence of the oscillator, for 

 although the imperfectly conducting surface of the , 



glass acted as a perfect screen from such action when '^ 



the potentials of the oscillator were varied slowly, it did not do 

 so for changes occurring about 500 million times per second. 

 After adopting means to avoid this disturbance, and construct- 

 ing lighter resonators, the experiments were repeated, with 

 negative results. From the dimension-^ of the quartz-fibre used 

 it was estimated that a force of 158 millionths of a grain 

 could have been detected with certainty ; this would have cor- 

 responded to about 7f Jix of an ampere in each resonator. It is 

 hoped that by further increasing the sensitiveness of the ap- 

 paratus, and using parabolic reflectors, the effect sought for may 

 be detected. In the second method of attacking the subject, a 

 Joule's dynamic air-thermometer was employed. This consisted 

 of a glass tube with a partition along the middle extending 

 nearly to the ends. If one side of the tube be warmed, convec- 

 tion currents circulate, and deflect an index placed in the steam. 

 A small mirror suspended about one edge, and counterpoised, 

 was used for an index, and was so sensitive that it was im- 

 possible to get the air still enough by any ordinary method of 

 screening. However, by the ingenious device of putting the 

 thermometer within a larger tube kept rotating by clockwork, 

 the difficulties were surmounted. A doubled wire placed in 

 one side of the thermometer served as resonator, and 

 on starling the oscillator a large deflection resulted. A 

 similar deflection was caused by applying about ^ of a volt to 

 the ends of the wire. This proved that the effect observed by 

 Mr. Gregory is due to heating. The least rate of heating ob- 

 servable with the air thermometer was found to correspond to 

 one calorie (gramme-water-Centigrade) per 24 hours in the whole 

 tube, or i calorie per centimetre of wire in 103 days. Dr. 

 Lodge asked Sir William Thomson whether, when electric 

 pulses travel along parallel wires with the velocity of light, any 

 action could exist between them, for two charged spheres 

 travelling together at that velocity exert no mutual attraction or 

 repulsion. In reply, Sir William said he was inclined to think 

 Mr. Boys's treatment of the subjection was in the main correct, 

 but it was quite possible that at such velocities the ordinary laws 

 might be modified by the fact that the time taken for the force 

 to be propagated from wire to wire is comparable with that 

 ■required for the pulse to travel the whole length of the wire. As 

 an example of the peculiar effects of rapid discharges, he said he 

 had seen two copper wires which had been flattened against 

 each other by lightning. Mr. Boys thought that in his resonators 

 a condition analogous to stationary waves would exist, for the 

 pulses are reflected from the ends. Dr. Lodge said he had 

 that afternoon observed the action of parallel strips when 

 Leyden-jar discharges were passed through them. The strips 

 gave a kick at each discharge. Mr. Gregory mentioned that, in 



NO. 1080, VOL. 42] 



trying to increase the sensitiveness of his meter so as to measure 

 the variation with distance, he had found that two resonators in 

 proximity interfered with each other. He had, however, suc- 

 ceeded in increasing the sensibility about five-fold. Prof. 

 Worthington asked if it was possible to mea'^ure the energy of 

 the oscillator, and also whether the quantity caught by the 

 resonator could be estimated from the solid angle it subtended 

 at the source of energy, wherever that might be. Prof. Perry 

 considered it easier to infer the energy of the source from that 

 received by the resonator. Dr. Lodge said the energy of the 

 source could be easily measured. The power radiated was 

 enormous whilst it lasted, vastly exceeding that of tropical sun- 

 shine ; and, if it could be made continuous, the apparatus would 

 soon be red-hot. The energy radiated, he said, converges on 

 the resonators, and hence the solid angle method of esti- 

 mating the amount received would be erroneous. Moreover, 

 th-? source was not at the oscillator, but at a quarter wave- 

 length from it, and most of the energy returns to the oscillator ; 

 only a small fraction is splashed off and sent into space. 

 Small oscillators radiate powerfully because the quarter wave- 

 lengths are small ; whereas the slow oscillators or alternators 

 used commercially radiate very little of their energy. The exact 

 law of variation of intensity of radiation with distance was 

 rather complicated, but the theory had been completely worked 

 out by Stokes in 1848. Mr. Blakesley thought the energy that 

 returns to the oscillator would be available for subsequent radia- 

 tions. Dr. Lodge pointed out that wires or other resonators 

 placed within the quarter wave-length would intercept part of 

 the returning energy. — Two communications — notes on second- 

 ary batteries, by Dr. Gladstone and Mr. Hibbert ; and an easy 

 rule for calculating approximately the self-induction of a coil, 

 by Prof. J. Perry — were taken as read. In the first of these the 

 authors show cause for believing that the beneficial effect pro- 

 duced by adding sodium sulphate to the ordinary electrolyte is 

 due partly to its facilitating the reduction of lead sulphate and 

 also to its power to diminish local aciion between the electrolyte 

 and different parts of the lead plates. As regards the chemical 

 actions which take place during the working of ordinary cell?, 

 they see no reason to doubt the view put forward by one of them 

 in 1882, that the substance produced in the voltaic reaction is 

 ordinary lead sulphate, PbSOj. They also conclude that the 

 high E.M.F. of a cell immediately after stopping the charging 

 current is due to the inequality of acid strength near the two 

 plates, and the gradual fall of E.M.F. is caused by the equaliza- 

 tion of strength produced by diffusion. — Prof. Perry's rule relates 

 to hollow cylindrical coils, and is expressed by the following 

 formula: — 



T ,. v \ «"«^ -r- 10^ 



L (m secohmsi = ^ ■ ; 



r844a -f yic + isb 



where n = number of windings, 



a — mean radius of winding in centimetres, 



i? = axial length, 



c = radial depth of winding, 



and d and c are less than -. 

 2 



The time-constant of such a coil is given in terms of the volume 

 of copper (V) in cubic centimetres by 



L _ V -f- 1000 . 



R " o728a^ i-33<r -h i"S(^ ' 

 and the conditions for making this small are pointed out in the 

 paper. — A paper by the Rev. T. Pelham Dale was postponed 

 till next meeting. 



Anthropological Institute, June 10. — Prof. Flower, C.B., 

 F.R.S., Vice-President, in the chair. — The Chairman exhibited 

 a " ula" or fetish brought by the Rev. L. O. Warner from the 

 neighbourhood of Lake Nyassa. — Mr. Theodore Bent read a 

 paper on the nomad tribes of Asia Minor. The paper referred in 

 the first place to the heterogeneous mass of nationalities on and 

 around the Cilician plain, but took only one point for discussion 

 — namely, the religion of the Ausairee around Tarsus, identifying 

 this cult with that of the Ali-ullah-hi of Northern Persia, and 

 proving that most nomads, from the Mediterranean to the Caspian, 

 iDclonged to this secret religion- The dogmas of the religion 

 were set forth as obtained from three sources, namely : (i) account 

 of the renegade Suleiman ; (2) studies amongst the Ali-ullah-hi ; 

 (3) researches amongst the Ausairee of Tarsus. — The Rev. E. F. 

 Wilson read a few notes on some North American Indians. — 



