324 SIR JAMES HALL on the Consolidation of the Strata. 



but the lower portion of the sand had formed itself into a solid 

 cake. 



On allowing the whole to cool, after it had been exposed to 

 a high heat for many hours, and breaking up the mass, I was 

 delighted to find the result, occupying the lower part of the 

 pot, possessed of all the qualities of a perfect sandstone, as may 

 be seen in the specimens now presented to the Society. When- 

 ever the heat was not maintained so long, the sandstone which 

 resulted was less perfect in its structure, tasted strongly of salt, 

 and sometimes crumbled to sand when placed in water. 



Many of these early experiments were accomplished with to- 

 lerable success. But still the result was somewhat precarious, 

 and could not be announced with the confidence that I felt in 

 presenting my former experiments to this Society. 



The cause of this uncertainty I traced to the chemical ope- 

 ration of the salt, acting as a flux upon the porcelain vessels em- 

 ployed. This very action, I was well aware, was the main agent 

 and cause of our success, when kept within proper bounds ; but, 

 on being allowed to pass those limits, and to act on the contain- 

 ing vessel as well as on the experiment, it destroyed the vessel, 

 and converted the whole into a confused mass of slag. 



After numberless unsuccessful attempts, and after returning 

 again and again to the charge, with an interval sometimes of 

 years, I at last met with a quality in some of the materials to me 

 altogether unlocked for, by means of which may be obtained suc- 

 cessful results, with scarcely any risk of failure. 



I found that the action of the salt upon the substances of the 

 crucibles of clay, did not exert itself in the same manner upon 

 iron; but that a large vessel of cast-iron, 18 inches deep by 10 

 wide, and a common gun-barrel welded up at the breech, and 

 open at the top, enabled me to work with the heat of melting 

 gold, without injuring the vessels, and at any time to produce a 

 perfect freestone ; thus satisfying our theoretical expectations. 



