1877.] 



Supersaturated Saline Solutions. 



533 



when from a damp one they vary, although the conditions are apparently 

 the same. For example, one day last summer, when the wind was 

 westerly, and there was a bright warm sun occasionally obscured by 

 clouds, I placed twelve watch-glasses on a parapet wall in my garden, 

 and poured into them, while still warm from the boiling, a solution of 

 sodic sulphate (2 salt to 1 water). In the course of about twenty 

 minutes four of the solutions crystallized in large crystals of the normal 

 salt, with interposed liquid not supersaturated ; four formed thin crys- 

 talline needles, which started from a radiant-point as from the action of 

 a nucleus ; and the remaining four, which remained liquid, were touched 

 on the surface with a needle dipped in olive-oil, and they crystallized in 

 the pulpy form from the point. 



I think the foregoing details go some way to prove that supersaturated 

 saline solutions behave differently among themselves and to different 

 bodies under varying atmospheric conditions. If so, many contradictory 

 details connected with this subject are on the road to reconciliation. A 

 supersaturated saline solution in a closed flask in which the air is saturated 

 with moisture is in a different condition (at least as regards surface-tension 

 and the power of spreading the drop of oil into a film) as compared with 

 a similar flask loosely covered and in the open ah' on a fine day ; so that 

 an oil <fcc. introduced into the closed flask, as in M. Viollette's and Mr. 

 Liversidge's experiments, may be inactive, while under the other condi- 

 tiou the same oil may be active. One fine day in August I placed four 

 flasks containing sodic sulphate solution (2 to 1) in the open air, and let 

 fall from a dropping-tube (just taken out of water and put into ether) a drop 

 of ether on the surface of each. It was striking to see, from the cohesion- 

 figure of the ether, long lines of crystals radiating to the sides and bottom 

 of each flask. A fifth flask of the same solution was treated some days 

 later in my laboratory with a drop of ether ; but this was inactive, and 

 the solution did not crystallize until the flask was inverted against my 

 thumb. On a day in September, when the wind was S.E., I let fall into 

 each of four flasks containing a similar solution a drop of paraffine-oil 

 (marked " lubricating "). It formed a well-shaped lens on each surface 

 without any separation of salt ; but on gently shaking each flask, so as 

 to break up the lens, there was a sudden crystallization, and the normal salt 

 was produced in all four flasks. Some hours later I repeated the experi- 

 ment in my study with five flasks of a similar solutiou. The oil spread 

 upon all five surfaces and the solutions crystallized immediately, the 

 normal salt being again produced. I have hundreds of such cases in my 

 note-books which have supplied material for former papers ; but in 

 referring to them no discredit is intended to be cast upon the negative 

 results obtained by other observers who deny that oils, ether, &c. have 

 any nuclear action. I would suggest that in my numerous experiments, 

 carried on during several years, it is not probable that there was always 

 a lurking fallacy in the shape of a crystal of the same kind as that of the 



vol. xxvi. 2 v 



