Some Thermal and Volume Changes attending Mixture. 495 



rings will be wholly without action on one another. If, then, 

 such similar rings be placed parallel and close to each other, 

 they do not repel each other, as they should do if there existed 

 a repulsion between parallel lines of force. 



Practically, it is impossible to obtain rings so uniformly 

 forged and wound as to be entirely without external magnetic 

 action. This usually manifests itself as a slight polarity, which 

 is easily recognized by a compass-needle, the poles being at 

 the extremities of a diameter. But in my rings this polarity 

 has always been small, even when the induction in the ring 

 was 10,000 or thereabouts. I have suspended two such rings 

 parallel to each other by strings, and made the contacts by 

 the ends of the coils dipping into mercury. But neither by 

 reversing the magnetism of the rings relatively to each other, 

 nor by make and break have I ever been able to cause the 

 smallest movement of the nature of approach or recess of the 

 rings with reference to each other ; and this was only to be 

 expected from what is well known. 



We may notice that, in the illustration of Faraday, the 

 movement of the system of two parallel needles due to their 

 repulsion leads to a redistribution of the lines of force. It 

 appears therefore that the repulsion here observed must depend 

 upon this redistribution. To illustrate what is meant, suppose 

 the lines of force to exert their tension like elastic bands on a 

 mechanical system such that, when yielding to the tension 

 takes place, the needles are separated. In this case, whenever 

 the lines of force are prevented from changing their form, the 

 repulsion at right angles to them must disappear ; and this 

 appears to be what actually happens. 



LVII. On some Thermal and Volume Changes attending 

 Mixture. By Frederick Guthrie*. 



[The paragraphs are numbered in sequence with those of my previous 

 communications on Salt-Solutions and Attached Water.] 



§ 256. TT may be taken as a rule that solid crystalloids are 

 JL more soluble in liquids when the two are at a 

 higher than when at a lower temperature. The apparent 

 exceptions to this rule are all, I believe, referable to the de- 

 composition by heat which the solids undergo and the inferior 

 solubility of the new products in the liquid. 



In §§238-241 a it was shown that the liquids triethylamine 

 and water are remarkably more miscible when cooler than 

 when warmer ; and their relationship in this respect was 



* Communicated bv the Physical Society. Read November 8, 1884. 



