328 SIR JAMES HALL on the Consolidation of the Strata, 



follow up, by actual experiment, what I have thrown out as mere 

 matter of speculation. 



I conceive that salt, in the state of fumes, and urged by a 

 powerful heat, possibly also modified by pressure, or perhaps 

 combined with other substances, may have penetrated a great 

 variety of rocks, acting as a flux on some, as in basalt, granite, 

 &c. ; agglutinating others, as in the case of sandstone, pudding- 

 stone, &c. ; softening others, as in the case of contorted strata 

 of greywacke. In many cases, too, I conceive that these fumes 

 may have had the power of carrying along with them various 

 other materials, such as metals in a sublimed state, which would 

 in this way be introduced into rents, veins, and cavities, or may 

 even have entered into the solid mass of the rocks, which I ima- 

 gine these fumes may have had power to penetrate. I have 

 already tried some experiments in pursuit of these ideas. Salt, 

 for instance, has been mixed with oxide of iron, reduced to fine 

 powder, and then exposed to heat along with quartzose sand 

 The iron, I found, was borne up along with the salt fumes. 

 The sandstone, formed in this way, was deeply stained with iron, 

 and other most curious appearances presented themselves. 



Every one who has seen a sandstone quarry, must have no- 

 ticed evident traces of iron, the rock being stained in a great va- 

 riety of ways ; sometinfes in parallel layers, sometimes in con- 

 centric circles, or rather in portions of concentric spheres, like 

 the coats of an onion,-*-and, generally speaking, disposed in a 

 way not accountable by deposition from water. All these ap- 

 pearances I would account for, by supposing the rock, either at 

 the moment of its agglutination into sandstone, or at some sub- 

 sequent period, to have been penetrated by the fumes of salt, 

 charged with iron, also in a state of vapour. 



I may mention one very curious result of my experiments 

 with salt and iron, acting upon sand, namely, that, upon break- 

 ing up the specimen of artificial sandstone, an appearance often 



