1872.] 



on Supersaturated Saline Solutions. 



319 



films with immediate crystallization of the solutions, viz. pale seal-oil, 

 sperm-oil, cotton-seed oil, and niger-oil. A drop of linseed-oil formed a 

 lens ; hut this soon becoming ragged, crystals diverged from it. A drop of 

 castor-oil formed a lens with no nuclear action. 



Experiment 11. Three of the above solidified solutions were heated over 

 a lamp, boiled and covered over. The oil collected on the surface in in- 

 numerable small disks. Next morning one of the solutions was found 

 crystallized, and the other two became solid on gently agitating the flasks. 



In this case as the solutions cooled down or were gently agitated the 

 disks spread out into films with nuclear action. 



Experiment 12. A solution of 3 parts salt to 1 of water was filtered 

 into twelve flasks, when a drop of each of the following oils deposited on 

 the surfaces of the solutions became lenticular without any separation 

 of salt, viz. pale seal-oil, olive- oil, rape, castor- oil, croton-oil, niger, sperm, 

 and cotton-seed oil. 



So far this result is in accordance with the theory. 



Experiment 13. A solution of the same strength as in the last experi- 

 ment was employed, when a drop of seal-oil, sperm, cotton-seed, and niger 

 spread out into films with powerful nuclear action. Linseed- and castor- 

 oil formed lenses with no such action. 



Now it must be remarked that on the day when Exp. 1 2 was made the 

 weather was dull, damp, and cloudy, and during the time of Exp. 13 the 

 weather was bright and clear. Some years ago it was a matter of frequent 

 observation to one of us, that the formation of cohesion-figures on the sur- 

 face of water was much more rapid and decisive, with altogether finer and 

 sharper results, in bright weather as compared with dull, damp, wet, or 

 foggy weather. The same remark applies to the motions of camphor 

 on water, and to those curious phenomena known as "camphor-cur- 

 rents" and " camphor-pulsations "*. In the production of all these phe- 

 nomena, as has been shown by one of usf, surface-tension plays a most 

 important part ; and such tension is lowered in dull foggy weather pro- 

 bably by the condensation of the vapour of volatile matters contained in 

 the atmosphere. A drop of a liquid under such conditions may not spread 

 on the surface of water or of mercury, the latter being especially liable to 

 such influences ; whereas oh a bright day such surfaces are particularly 

 active, and experiments succeed which some hours or days before failed to 

 produce the results expected. 



Then, again, as pointed out by one of us in Part II., the viscosity of the 

 surface, or of the drop of liquid placed upon it, may greatly interfere with 

 the operation of the law by which a liquid B spreads upon the surface A. 

 A supersaturated saline solution has a considerable viscosity of surface, 

 which it retains for many hours after it has cooled down. In the course 

 of about twenty-four hours the more watery particles come up to the sur- 

 * Phil. Mag. for Dec. 1869. 



t Sur la Tension superficielle des Liquides, par Gr, Yan der Mensbrugghe, 

 VOL. XX. 2 c 



