May 23, 1889] 



NATURE 



93 



other atomic weights) was devised by which the normal salt 

 could be obtained free from acid on the one hand, and from 

 basic salt on the other. In order to have a sufficient check on 

 the results, the carefully purified zirconia was further treated 

 by four perfectly independent methods, 



(a) The sulphate was prepared and its solution precipitated 

 by means of hydrogen peroxide. 



[b) The tetrachloride was prepared and its solution pre- 

 cipitated by ammonia. 



(f) The sulphate was re crystallized several times from con- 

 centrated sulphuric acid and precipitated by ammonia. 



(d) The oxychloride was prepared and recrystallized and 

 precipitated by ammonia. 



The average values obtained from the sulphate prepared 

 from the specimens of zirconia so treated by determining the 

 relation Zr(S04).2 : ZrO,, were : — 



is the same as that in (2), the impulse given to the charged 

 body by destroying the induction will be — 



(a) 90*402 

 {b) 90-390 

 {c) 90-471 

 {d) 90-30 



mean 90 "401. 



In addition to the investigation of the salts which have been 

 used in the estimation of the atomic weight, observations on 

 the peroxides of zirconium discovered by Cleve and the author 

 are embodied, as well as an examination of the so-called 

 metallic zirconium. 



" Determining the Strength of Liquids by means of the 

 Voltaic Balance." By Dr. G. Gore, F.R.S. 



This method is based upon the circumstance that the greater 

 the degree of concentration of a solution the larger is the amount 

 of dilution required to reduce its voltaic energy to a given magni- 

 tude. The method of measuring the energy is described in 

 Royal Society Proceedings, vol. xlv. p. 268, 



In the present research a known volume of solution was taken, 

 and the proportion of dissolved substance in it was found by 

 ordinary chemical analysis. A second portion was taken, its 

 specific gravity ascertained, and its degree of strength found by 

 aid of the ordinary published tables of specific gravities. A 

 third portion of known volume was then taken, its average 

 amount of voltaic energy measured, and its degree of concen- 

 tration ascertained by the amount of dilution required to reduce 

 its voltaic energy to the same magnitude ; the less dilute it was 

 at starting the greater the amount of dilution required. The 

 following are the results : — 



By HCI. H0SO4. HNO3. NaCl. NaaCOs- K3N. 



Chemical analysis ... 1-85 ... 5 60 ... 2-97 ... 9-13 ... 721 ... 1-05 

 Specific gravity ... 1-70 ... 5-44 ... 280 ... 8*74 ... 7-63 ... 1-03 

 Voltaic balance ... 1-65 ... 5-70 ... 2-90 ... 8-71 ... 7-57 ... i-o6 



A much less quantity of the substance is usually required by 

 the voltaic balance method than by either of the other ones, and 

 the operation is very quickly performed. 



Physical Society, May ir.— Prof. Reinold, President, in 

 the chair. — The following communications were read : — On an 

 electrostatic field produced by varying magnetic induction, by 

 Dr. O. J. Lodge, F.R.S. This paper describes a research 

 made with the object of finding some connection between static 

 electricity and magnetism. Several methods of attacking the 

 problem, such as rotating or varying the strength of magnets in 

 the neighbourhood of delicately suspended charged bodies, are 

 indicated, and the one selected was based on an idea of Mr. A. 

 P. Chattock, who conceived that a charged body in the vicinity 

 of a closed magnetic circuit would be affected by varying the 

 magnetic induction. From the theory of the effect it is shown 

 that the magnitude of the quantity sought is exceedingly small, 

 for the expression involves the inverse squr.re of the velocity of 

 light. The E.M.F. induced in any closed curve round the 

 magnetic circuit or solenoid by varving the induction, I, is given 

 by— 



dl 

 '^Ift (') 



If an E.M.F., e, act on 'a charge, Q, at distance r from the 

 axis of the solenoid, the work done in one revolution will be 

 «Q, and 



fQ = F . 27r^- (2) 



where F is the mechanical force. Now if the E.M.F. in (i) 





Ydt^n 



Z-irr 



(3) 



Since I = "^"""^^^ = /xC times a length, and Q = jV = KV 

 times a length, 

 .-. d> = KmCVA /iength)2 and K/* = --,, ,; , -. (^ oc _1_ 



The magnetic circuit actually used was a wire Gramme ring of 

 trapezoidal section, wound with copper over only a part of its 

 periphery. The indicating apparatus was a suspended needle, 

 consisting of two oppositely charged bodies carried on a small 

 shellac arm, to which a mirror or pointer was attached, and 

 was suspended vertically in the plane of the ring. Great dif- 

 ficulty was experienced from Foucault's currents when metallic 

 films were used for the needle, and the magnetic properties and 

 other semi-conductors tried further complicated the matter. 

 Eventually, the charged bodies were made of paper, in the form 

 of cylinders one- eighth of an inch diameter and three-eighths 

 of an inch long. Considerable trouble was caused by the elec- 

 trostatic action between the needle and exciting coils, and various 

 methods of screening were tried and abandoned, and subse- 

 quently the wire was replaced by a single spiral of copper rib- 

 bon, the outer turn of which was put to earth. Observation was 

 rendered difficult, owing to the wandering of the zero when the 

 needle was charged, but this was minimized by suitably shaping 

 the contour of the needle's surroundings. Heat also created 

 considerable disturbance, and the convection currents were cut off 

 by a series of concentric cylinders of tin plate. The method of 

 observation was to charge the two insulated parts of the needle, 

 and then reverse the magnetizing current in synchronism with 

 the period of the needle, noting whether the amplitude of any 

 residual swing could be increased or diminished according as 

 the impulse assisted or opposed the motion. In this way, slight 

 indications have been observed, and the effects reverse when the 

 charges of the cylinders are reversed. In explaining the theory 

 of the experiment, the author made use of a simple transformer, 

 consisting of an ordinary hank of iron wire wound over with 

 insulated copper and provided with several secondary coils ; and 

 by it he demonstrated that the primary current increases on 

 closing the secondary, due, as was shown, to the decrease of 

 self-induction of the primary caused thereby. Prof. Fitzgerald, 

 in answer to a question from Dr. Lodge as to the influence of 

 screens, said he had not fully considered the matter in this par- 

 ticular case, and, as the general effect of screens depended on 

 the square of "z',"the subject required careful treatment. As 

 a means of checking the results obtained by Dr. Lodge, he sug- 

 gested calculating the impulse, and seeing whether its magnitude 

 approximately corresponds with that observed. Commenting 

 on an idea for carrying out a similar experiment attributed to 

 him in the paper, in which a charged gold leaf is placed between 

 the poles of a magnet, Prof, Fitzgerald said he had been mis- 

 understood, for he had conceived a disk parallel to the faces of 

 the magnets, which, when excited, should cause the disk to turn 

 in its own plane. Referring to the equations for mechanical 

 force given in Maxwell, §619, he pointed out that the coefficieat 

 of e in the equation — 



, (/(// da 



- inv - c~r- - m j- 



dx dx 



X 



ought to be P, where- 



d¥ 



r> . ,. av 



^ = cy-bz- -^ - 



d^ 

 dx' 



and considered it very important that the existence of the 

 term e - should be tested experimentally. Prof. S. P. 



Thompson mentioned some experiments on which he was 

 engaged by which he hoped to show electric displacement in 

 continuous dielectric circuits, such as a link of gutta-percha. 

 Up to the present the experiments had not been successful^ 

 owing to his inability to place the two Gramme ring coils used 

 into such relative positions as to give silence in the telephone 

 connected with the coil used as secondary, when currents were 

 sent through the primary. Prof. Ayrton suggested that Dr. 

 Thompson's difficulty may arise from the fact that such rings do 

 produce considerable external field, even when carefully wound. 



