376 



Mr. E. B. H. Wade. On a new Method of 



10 seconds, unless the molecule itself is considered. This effect has 

 been observed in laminated specimens. 



The difficulty of working with alternate currents, if the core be 

 subdivided, in order to investigate the effects observed, using the 

 method in the ' Proceedings of the Roval Society,' vol. 53, p. 352, is 

 the necessity for the very accurate control and measurement of the 

 magnetising force. Small variations of this force would at once mask 

 the effects observed. In the paper just mentioned a considerable 

 difference was observed between cyclic curves obtained with the 

 ballistic galvanometer and by means of alternate currents having 

 frequencies of 72 and ] 25 per second in the case of a laminated hard 

 steel ring for maximum B = 16,000. On the other hand, no such 

 difference was observed in the case of a laminated soft iron ring when 

 maximum B was 4000.* It would seem from the experiments in 

 this paper that the amplitude of induction would not be so great for 

 high frequency and small induction density B, and this is of import- 

 ance in the case of iron cores for transformers. It is worth noting 

 that when working on solid rings with the ballistic galvanometer 

 induced curreDts may account for apparent magnetic instability. 



Mr. H. H. Hodd has helped me in the experimental part of this 

 paper, and I here wish to tender him my thanks. 



4< On a new Method of Determining the Vapour Pressures ot 

 Solutions." By E. B. H. Wade, B.A. Communicated by 

 Professor J. J. Thomson, F.R.S. Read May 13, 1897. 



(Amplified Abstract, received December 22, 1897.) 



On a previous occasionf I gave some boiling points of salt solu- 

 tions under atmospheric pressure. As the dimensions of that abstract 

 made a full account of the experimental method impossible, I have 

 been given this opportunity, by the courtesy of the Council of the 

 Royal Society, of describing the apparatus and procedure by which 

 those results were obtained. 



§ 1. Difficulties to be overcome. 



The exact determination of boiling points of solutions has been 

 attended hitherto with a good deal of difficulty. The boiling point 

 of the pure solvent is first determined. Salt is then added, and the 

 boiling point is redetermined. The experiment consists, in fact, of 

 two parts, and the difficulty lies in making the circumstances in 

 which the first part of the experiment was carried out identical with 



* See £ Electrician,' September 9, 1892. 

 f ' Roy. Soc. Proc.,' vol. 61. pp. 285—287. 



