IV 



Sir James Hall 187 



so nobly occupied, and I abstained during the remainder of 

 his life from the prosecution of experiments which I had 

 begun in 1790." a 



The death of Hutton in 1797 allowed the laird of 

 Dunglass to resume the experiments on which he had been 

 meditating during the intervening years. Selecting samples 

 of " whinstones," that is, intrusive dolerites and basalts, 

 from the dykes and sills in the Carboniferous strata around 

 Edinburgh, he reduced them in the reverberatory furnace 

 of an iron-foundry to the condition of perfect glass. 

 Portions of this glass were afterwards re-fused and allowed 

 to cool very slowly. There was thus obtained " a substance 

 differing in all respects from glass, and in texture com- 

 pletely resembling whinstone." This substance had a 

 distinctly crystalline structure, and Hall gave it the name 

 of crystallite, which had been suggested by the chemist, 

 Dr. Hope. 



Before he was interested in the defence of the Hut- 

 tonian theory, Sir James had made a journey into Italy in 

 the year 1785, visiting Vesuvius, Etna, and the Lipari 

 Isles, and having for part of the time the advantage of the 

 company of Dolomieu. He could not help being much 

 struck with the resemblance between the lavas of these 

 volcanic regions and the familiar " whinstones " of his own 

 country. So close was this resemblance in every respect 

 that he felt " confident that there was not a lava in Mount 

 Etna to which a counterpart might not be produced from 

 the whinstones of Scotland." At Monte Somma he noted 

 the abundant " vertical lavas " which, in bands from two 



1 For Hall's papers see Trans. Roy. Soc. Edin. iii. (1790), p. 8 ; v. (1798), 

 p. 43 ; vi. (1812), p. 71 ; vii. (1812), pp. 79, 139, 169 ; x. (1825), p. 314. 



