NATURAL HISTORY OF THE EIGHTEENTH CENT. 413 



The present structure of our planet is, according to Hutton, the 

 remains of a former world ; our present continents are formed out of 

 the ruins of former continents washed down to the bottom of the ocean, 

 there compacted, and again upheaved after the lapse of ages ; some- 

 times changed by subterranean heat, or fractured, or bent and contorted. 

 The forces which reduced the materials of the ancient continents to 

 the condition of mere sediment subsiding to the bottom of the ocean 

 are still at work, destroying even the hardest of the existing rocks, 

 transporting their debris to the sea, and spreading it out on the floor 

 of the deep, to form new strata like those of former times. 



Hutton was convinced that basalt and many other kinds of trap-rock 

 had been originally ejected from below, and had penetrated fissures 

 of the sedimentary rocks, and he succeeded in discovering ocular de- 

 monstrations of the truth of this surmise, by finding in Glen Tilt, in 

 1 785, veins of red granite diverging from the principal mass and intersect- 

 ing the stratified rocks. What now became of the doctrines of Werner 

 and of preceding geologists, who had declared that granite was the oldest 

 of all the rocks ? Glen Tilt showed that so far from granite having been 

 the primordial substance or nucleus of our planet, it was more recent 

 than the strata derived from still older rocks; and might not these 

 be themselves the results of a cycle of changes like that to which our 

 present rocks are traceable, and so on ad infinitum ? Again, may not 

 granite itself, now proved less ancient than the strata containing organic 

 remains, be simply the result of the fusion of some rock originally 

 sedimentary, but lying the deepest in the series, and fused by the 

 intensity of the internal heat ? 



According to Hutton's theory, the cycles of destruction by aqueous 

 agencies, rearrangement, consolidation, and upheaval by igneous 

 actions, have continued and will continue indefinitely. His system im- 

 plied a duration of earth through a reriod of time, vast indeed com- 

 pared with the six thousand years or thereabouts which had commonly 

 been supposed to have elapsed since the universe came into being as 

 we now see it,, after its gradual formation had occupied the short period 

 of time represented by one hundred and forty-four hours in our pre- 

 sent mode of computing time. " In the economy of the world, I can 

 find no traces of a beginning, no prospect of an end," said Hutton, 

 reading the testimony of the rocks to the best of his ability. Theo- 

 logians took the alarm, and declared that it was Hutton's object to 

 invalidate revealed truth by reviving the doctrines of some pagan phi- 

 losophers concerning an eternal succession. Dr. Playfair, who illus- 

 trated and explained Hutton's doctrines, remarks on the attacks which 

 had been made upon Hutton on other than scientific grounds, and 

 particularly with regard to this passage, that, " In the planetary mo- 

 tions, where geometry has carried the eye so far, both into the future 

 and the past, we discover no mark either of the commencement or 

 termination of the present order. It is indeed unreasonable to sup- 



