248 HEROES OF SCIENCE. 



These judgments might be erroneous in cases 

 which required the knowledge of other data, not 

 then collected, for a true and general solution ; but 

 the very unreasonableness of raising the standard 

 of his own discoveries in a limited region, for con- 

 demning a speculation perhaps founded on other 

 truths occurring elsewhere, shows how firmly these 

 discoveries, and the influences belonging to them, 

 were established and fortified in his mind. The 

 following passage, written in January, 1796, might 

 have been acknowledged by the author to contain 

 his real opinions forty years later : — 



" Therefore every man of prudence and obser- 

 vation who has paid the strictest attention to 

 mineralogy, the structure of the earth, and the 

 changes it has undergone, will be very cautious 

 how he sets about to invent a system which nature 

 cannot conform to without having recourse to 

 subterraneous fires, volcanic eruptions, or un- 

 common convulsions, by which every hill and dale 

 must have been formed and every rock must 

 have been rent to form those chasms, which, 

 in comparison to the strata they are found in, are 

 no more than sun-cracks in a clod of clay ; yet 

 such has been the language of ingenious men, who 

 have set their theoretical worlds a-going without 

 either tooth or pinion of nature's mechanism 

 belonging to them." 



In October and November of this year (1796), 

 we find him returning to the contemplation of 

 organic remains ; discussing the circumstances 



