116 GEOLOGICAL CHANGE, AND TIME. 



dice Hall deliiyed to carry out his intention during Button's lifetime. 

 But afterwards lie instituted a remarkable series of researches which 

 are memorable in the history of science as the first methodical endeavor 

 to test the value of geological speculation by an appeal to actual ex- 

 periment. The Neptuuists, in ridiculing the Huttonian doctrine that 

 basalt and similar rocks had once been molten, asserted that, had such 

 been their origin, these nuisses would now be found in the condition of 

 glass or slag. Hall however triumphantly vindicated his friend's \\e\v 

 by proving that basalt could be fused, and thereafter by slow cooling- 

 could be made to resume a stony texture. Again, Hutton had asserted 

 that under the vast pressures which must be effective deep within the 

 earth's <*rust, chemical reactions must be powerfully influenced, and 

 that under such conditions even liniestoue may conceivably be melted 

 without losing its carbonic acid. Various siiecious arguments had 

 been adduced against this proposition, but by an ingeniously devised 

 series of experiments Hall succeeded in converting limestone under 

 great pressure into a kind of marble, and even fused it, and found that 

 it then acted vigorously on other rocks. These admirable researches, 

 which laid the foundations of experimental geology, constitute not the 

 least memorable of the services rendered by the Huttonian school to 

 the progress of science. 



Clear as was the insight and sagacious the inferences of these great 

 masters in regard to the history of the globe, their vision was neces- 

 sarily limited by the comparatively narrow range of ascertained fact 

 which up to their time had been established. They taught men to 

 recognize that the present world is built of the ruins of an earlier one, 

 and they explained with admirable perspicacity the operation of the 

 processes whereby the degradation and renovation of land are brought 

 about. But they never dreamed that a long and orderly series of such 

 successive destructions and renewals had taken place and had left 

 their records in the crust of the earth. They never imagined that from 

 these records it would be possible to establish a determinate chro- 

 nology that could be read everywhere and ap'iilied to the elucidati<m 

 of the remotest quarter of the globe. It was by the memorable obser- 

 vations and generalizations of William Smith that this vast extension 

 of our knowledge of the past liistory of the earth became possible. 

 While the Scottish philosophers were building up their theory here, 

 Smith was (juietly ascertaining by extended journeys that the stratified 

 rocks of the west of England occur in a definite sequence, and that 

 each well-marked group of them can be discriminated from the others 

 and identified across the country by means of its inclosed organic 

 remains. It is nearly a hundred years since he made known his views, 

 so that by a curious coincidence we may fitly celel)rate on this occasion 

 the centenary of William Smith as well as that of James Hutton. No 

 single discovery has ever had a more momentous and far reaching in 

 llueuce on the progress of a science tliaii that law of organic succession 



