ON THE EFFECTS OF LONG-CONTINUED HEAT. 185 



mountain chains culminated to their utmost height. In the progress of re- 

 frigeration the compressing and imprisoned forces became nearly balanced, 

 and the residual predominance of the latter produces the phenomena of 

 existing earthquakes and volcanoes. 



In the earlier periods, unmutilated skeletons, undisplaced scales, entire 

 ink-bags, and florescent fronds, indicate conditions of nature which would 

 now be called unnatural, a history of sudden death and speedy embalment, 

 common, not to individuals only, but to generations and species. The pre- 

 servation, in exquisite casts, of the most delicate organizations indicates a 

 speedy but a tranquil entombment, which it would be difficult to refer 

 to any other agency than that of gaseous emanation through the waters 

 in which the plants and animals existed. Alcyonia and sponges, looking 

 like recent specimens preserved in the places where they grew, point to a 

 process of silicification, chiefly anhydrous, which anticipated decomposition. 

 In the decreasing activity of internal heat and insalubrious emanations, we 

 see the advancement of the physical and chemical conditions essential or 

 advantageous to life; and with the progress of such conditions, favourable to 

 the development of higher and higher forms of organization, we find a perfect 

 correspondence in the natural history of organized fossils, and the increasing 

 tones of the " Diapason, closing full in Man." 



From the theory of heat and the facts of geology, combined with physio- 

 logical considerations, we learn that there was a definite era, in which the 

 earth first became capable of supporting vegetable and animal life ; and we 

 may account for the late appearance of man, by observing that there were no 

 conditions adapted to the well-being and progress of human nature, till this 

 state of things had yielded to a healthy atmosphere, a moderate heat, 

 differentiated zones of life, stable forces, and a stationary standing ground. 



In the rudimental ages of the earth we behold an ever-changing scene of 

 new and fitful conditions passing in rapid succession. Through all the stages 

 of its existence previous to the present uniformity, so favourable to the 

 exercise of reason and the freedom of will and action, we see force gradually 

 subsiding, and the time allowed to life expanded into a wider liberality. Our 

 ideas of its duration, as compared with indefinite ages, are equally limited with 

 our view of its magnitude, in comparison with space or matter ; we can find in 

 geological data no chronology but that of priority; the fossil records even of 

 its unconsolidated beds have not yet supplied us with the key of the cypher 

 which should connect geology with human history. If ever we come to know 

 the age of the primary rocks, or of the protozoic strata, it can only be by 

 combining physical data with the experimental reproduction of granite, and 

 a knowledge of the heat which the lowest organisms can bear, and live. 



Since Hall first applied chemistry to the service of geology, few attempts 

 have been made in this country to pursue the path which he opened. In 

 1833 the British Association entrusted to a commission, consisting of Prof. 

 Sedgwick,Dr Daubeny.the late Dr. Turner,and myself, the task of illustrating 

 geological phenomena by experiments which it was hoped might have thrown 

 light on some of the subjects discussed in this Report. Disappointed of the 

 greater part of the fruit of these experiments, I yet believe that the few 

 results which I now lay on the table of the Section will not prove devoid of 

 interest, especially as evidence of the low temperature at which bodies scarcely 

 reputed volatile are capable of being sublimed. 



The iron furnaces of Yorkshire having been selected as furnishing the 

 best field for these experiments, it fell to my lot to conduct them. Every 

 facility was afforded me by the zeal and liberality of the proprietors and 

 managers of two furnaces, one of which at Elsicar, belonging to the late Earl 

 Fitzwilliam, and managed by Mr. H. Hartop, worked for a period of five 



