SIR JAMES HALL on the Consolidation of the Strata. 323 



the principles of latent heat. To put this to the test, I pro- 

 ceeded to expose a quantity of sand, covered to the depth of 

 several inches with common salt-water, to the heat of a furnace, 

 and, as the liquid boiled away, replenished it from time to time 

 by additions from the sea. Of course it gradually approach- 

 ed to a state of brine. But this proved a very tedious operation, 

 requiring a continued ebullition, during three weeks without 

 ceasing, before it became sufficiently saturated with salt by the 

 discharge of the fresh-water ; and I thought it much easier, and 

 no less satisfactory, to employ brine from the first, formed at 

 once by loading the water with as much salt as it could dissolve, 

 amounting to about one-third of its weight. 



The vessels employed in these early experiments, were the 

 large black-lead crucibles used by the brass-founders. I filled 

 the vessel, which was 18 inches high and 10 broad, nearly to the 

 brim with brine of full saturation, the lower portion being occu- 

 pied, to the depth of about 15 inches, with loose sand from the 

 sea-shore, and thoroughly drenched with the brine. In order to 

 have a view of the progress of the experiment, I placed an 

 earthen-ware tube, about the size and shape of a gun-barrel, 

 closed at bottom, and open at the top, in a vertical position, ha- 

 ving its lower extremity immersed in the sand, and reaching to 

 within about an inch of the bottom of the pot, while the other 

 end rose a foot above the surface of the brine, and could be 

 looked into without inconvenience. 



After a great number of experiments, furnishing an unbound- 

 ed variety of results, I at length obtained a confirmation of the 

 main object in view. I observed that the bottom of the porce- 

 lain barrel, and of course the sand in which it rested, became 

 red-hot, whilst the brine, which, during the experiment, had 

 been constantly replenished from a separate vessel, continued 

 merely in a state of ebullition : the upper portion of the sand, 

 drenched with the liquid, remained permanently quite loose, 



