1879.] Mr. G. Tomlinson on the Action of Nuclei. 



327 



Many examples are given in which oils, fixed and volatile, alcohol, 

 ether, &c, spreading on the surface of the solution, lead to the separa- 

 tion of salt, and the solidification of the solution ; while, if such liquids, 

 instead of spreading, assume a lenticular form, they become inactive, 

 and by shaking the flask with a circular motion, are dispersed through 

 the solution in numerous globules, without any immediate nuclear 

 action. 



There are several circumstances which favour the action of these 

 liquid nuclei, such as (1) chemically clean flasks and solutions, so as to 

 maintain (2) the surface-tension of the solution as high as possible, in 

 order to spread the oils; (3) bright and clear weather, with strong 

 evaporative force. Under such conditions the oils, &c, usually form 

 .films with nuclear action. 



But it has been shown that in closed flasks, with special precautions 

 against the entrance of particles from the air, the oils, &c, may be 

 made to spread on the surface of these solutions without any nuclear 

 effect. 



The negative results arrived at by M. Viollette, Mr. Liversidge, and 

 other eminent observers, led them to conclude that oils, alcohol, 

 ether, &c, as well as porous bodies, have no action whatever on these 

 solutions, and that the only nucleus is a salt of the same kind as the 

 one in solution, or isomeric therewith ; and that, when the oils, &c, 

 appear to act they really contain particles of such a salt ; or when the 

 flask is uncovered for the purpose of introducing the oil, &c, such a 

 saline speck enters from the air, which is supposed to contain saline 

 nuclei floating about in it. 



The objections made to my mode of experimenting, as well as to my 

 conclusions, were fair enough, since, if my experiments always con- 

 tained a flaw, the conclusions drawn from them would be worthless. 

 But the thousands of results, recorded in my note books, are suffici- 

 ently harmonious to satisfy me that my mode of experimenting is 

 trustworthy ; nevertheless, I have to account for the results and con- 

 clusions of other observers which stand in direct opposition to mine. 



It was a long time before I could hit upon a right method of pursu- 

 ing the inquiry. At length I was led to make a number of observations 

 daily, during some months, on the action of a freshly- distilled volatile 

 oil on solutions of sodic sulphate, and found that during certain 

 winds the oil was active, and that, while other winds prevailed, it was 

 passive.* 



It was clear then that, during some winds, a force was present in 

 the air which rendered the oil active ; while, during other winds, the 

 force being absent, the oil became passive. I succeeded in identify- 

 ing this force with ozone; and the point now to be determined is, 



* These observations were made at Highgate. Otlier observations by the sea-side. 

 &c, are noticed in ''Proc. Eoy. Soc.," vol. xxix, p. 24. 



