mtl 0f #icanw ^iwcttlatiatt gewerally, with 



»ifta( Mcmwt 0f Hit v^^t »f §.§i^^. 



(^Mlmpx. 



BY W. LANT CARPENTER, B.A., B.Sc. 



Head October 1st, 1874. 



[Abridged.] 

 rpHE attention of the Society was first drawn to a few simple 

 -*- physical principles, which entered largely into the 

 explanation of the causes of the currents in large masses of water. 

 The fundamental doctrine was that whenever the equilibrium of 

 the several parts of a mass of liquid were disturbed, their 

 inequality of pressure produced a movement for its restoration ; 

 and it followed from this, that if the disturbing cause continued 

 to act, there would be a constant tendency to restoration, without 

 an actual restoration of equilibrium, and hence a continuous 

 movement would be set up. The simplest case was the formation 

 of a *' head " of water by wind blowing towards the head of a 

 long inlet. Other causes were the alteration in the specific 

 gravity of water, either by changes in its temperature, or in its 



