﻿xlii PKOCEEDINGS OF THE GEOLOGICAL SOCIETY. 



52 atmospheres, equal to 1700 feet of sea ; 86, answering to nearly 

 3000 feet ; and 173, to 5700 feet of sea — that is, a little more 

 than a mile. The results were, that under the first of these pres- 

 sures the powder was changed into a compact limestone, under 

 the second to a marble, and under the last it underwent complete 

 fusion, and acted powerfully on other rocks. He states that on ex- 

 hibiting a specimen of the saccharoid marble to the workman he 

 employed to polish it, the man observed that, if it were a little 

 whiter, the quarry from which it had been taken would be of great 

 value. 



The soiuidness of the conclusions to which Hall arrived has been 

 lately called in question by Dr. Gustav Rose, Professor of Geology 

 in the University of Berlin, in a memoir published in the ' Monats- 

 bericht ' of the Berlin Academy for July last, giving an account of 

 two experiments on the effect of a powerful heat on earthy lime- 

 stone enclosed in a gun-barrel hermetically sealed, — experiments so 

 far analogous to some of those of Sir James Hall. The barrel was 

 placed in a newly erected gas-furnace, in which the heat was suffi- 

 ciently great to melt easily large masses of platina. He describes 

 the changes which the earthy limestone was found to have under- 

 gone, and thus concludes : — " From these experiments it would 

 appear that chalk and compact limestone, when subjected to a high 

 temperature in a closed space, are not changed into distinct crystalline 

 spar, and that, as a general fact, rhomboidal carbonate of linie is not 

 formed by the so-called dry process. When the descriptions of Hall's 

 experiments, as well as those which Bucholz afterwards made with 

 the same object, are examined, it appears extremely probable that 

 the results were what the authors describe, but that they mistook the 

 hard-baked but unaltered chalk for crystalline marble. Although 

 those experiments of Hall have been so much quoted, as affording 

 an explanation of geological phenomena, and in support of theoretical 

 views, they have not received any confirmation from having been 

 repeated by others ; and the experiments of the present author show 

 how hasty the general conclusions were which were drawn from 

 them." 



"With eveiy respect for my friend the Professor, I think that I 

 may turn round upon him and say that he has been somewhat hasty 

 in considering that his experiments prove that mistakes were made 

 by Hall in his descriptions of the results of his numerous experiments, 

 all agreeing while obtained in so many clifferent ways ; for the Pro- 

 fessor states that in both of his experiments the gun-barrel burst 

 (atwhat stage of the experiment, he does not say); and thus one of the 

 essential conditions in Hall's experiments was wanting, viz. continued 

 great pressure. I consider therefore that these experiments of Pro- 

 fessor Rose in no degree invalidate those of Hall, so long considered 

 to support, in no inconsiderable degree, the hypothesis of Hutton. 



In 1816 Professor Hausmann of Gottingen drew attention to the 

 explanation of geological phenomena by observations on some products 

 obtained from smelting-furnaces. Among the most remarkable re- 

 sults of the condensation of the vapours of smelting-furnaces is the 



