SATTSSURE. PALLAS. TOULMIN. 37 



as a guide to later observers, who, warned by his example, 

 first seek sufficient data before they presume to propose a 

 theory, and visit the scene of inquiry ere they attempt to 

 form a judgment as to the phenomena which it presents. 



Meanwhile DE SATJSSURE and PALLAS had arrived at 

 similar conclusions, by means of independent researches ; 

 the one by the exploration of Switzerland and the Alps, and 

 the other by that of Siberia and the Ural mountains, both 

 recognising the existence of internal heat, and its operation 

 in raising portions of the earth's surface into mountains. 



DE. TOTJLMIN'S Essay on the Antiquity of the World was 

 published about the year 1775, and affords an interesting 

 example of the progress of opinion : sentiments which little 

 more than half a century ago drew on their author the 

 opprobrium of being a sceptic, are now admitted as demon- 

 strable truths. He maintains that no single substance in 

 nature is either permanent or primary ; that the animals, the 

 vegetables, the earths, the stones, the minerals alike take 

 their origin in the gradual progress of time, and in its increas- 

 ing succession are alike exposed to innumerable transmuta- 

 tions ; that the globe itself, from a multitude of causes, is 

 subject to slow, but important revolutions; that it under- 

 goes incredible changes from heat and cold, volcanoes and 

 earthquakes; that vast alterations are gradually made by 

 the decay, generation, petrifaction, and other transmutations 

 of vegetables and animals ; that the sea is continually alter- 

 ing the surface of the earth ; that in the lapse of time, it 

 encroaches on the dry land, and takes it from its-inhabitants, 

 and restores it to them again ; and that gradual influences 

 occasion those numerous, but partial inundations which have 

 been found to make such deep and lasting impressions, and 

 have existed in every country, leaving behind them the most 

 visible marks of ruin and devastation. The conclusion of 

 the author is, that nature is invariably the same her laws 

 immutable and eternal. 



The above remarks convey the substance of the systems 

 of later philosophers. The first passage, which we have 

 distinguished by italics, contains the essence of the theory 

 of Dr. Hutton ; the second embodies some of the leading 

 principles which, recently enforced by Sir C. Lyell, were, 

 at an earlier period, advocated by Dr. Hutton and Professor 



