433 



Earl of Berkeley and Mr. E. G. J. Hartley. [Apr. 21, 



Final Form of Apparatus.— Wq had foreseen this defect, and a means 

 of overcoming it, should it mask the desired result, was suggested by 

 Dr. Burton, of the Cambridge Scientific Instrument Company. It con- 

 sisted in replacing the plate by a porcelain tube; surrounding the 



Eiq. 2. 



middle portion only by the solution and leaving the ends free. Thus, 

 when the pressure was applied to the solution, the compression of the 

 "dermatine" rings, which confine it, would have no effect on the 

 volume of water inside the tube. 



This is embodied in the final form of apparatus which is shown, in 

 vertical section, in fig. 2. 



