Pres iden t 's A ddr ess . 



113 



degredation of a former world the present strata have ori- 

 ginated. The second principle assumed in the Huttonian 

 theory is that the materials which are collected at the 

 bottom of the ocean are at great depths exposed to the action 

 of an intense heat, under very strong pressure, by which 

 they are fused and consolidated, so as to be capable of 

 forming new strata. The theory of Hutton was adopted by 

 Playfair, Hall, and others, in opposition to the Wernerian 

 views, at that time also vigorously upheld and taught by 

 Professor Jameson, formerly a pupil of the celebrated philo- 

 sopher of Freiberg ; and, indeed, the intellectual contest 

 carried on between the supporters of the rival systems is a 

 matter of history. In the Huttonian theory the old hypo- 

 thesis of a central heat became allied to the science of 

 geology, and was for a time a favourite theory with many 

 of our best writers, and used with great freedom, if not 

 license, by some practical and professional geologists. The 

 chief facts on which the speculation is based are the follow- 

 ing :— 



1st, The existence of volcanoes. 

 2d, Earthquake phenomena. 

 3d, Eocks of igneous formation. 

 ^tli, Thermal springs. 



5th, The increase of temperature in mines in proportion 

 to* their depth, and also in water in relation to the depth of 

 the strata from which it flows ; and, 



6th, The configuration of the earth. 



I. The Existence of Volcanoes. — The argument derived 

 from volcanoes in favour of a central heat rests mainly upon 

 the fact of the universal spread of volcanic activity over the 

 whole surface of the globe. They exist amongst the snows 

 of the Arctic regions and amongst the islands of the Southern 

 Ocean; in the south of Europe; in Central Asia, South 

 America, the West Indies, and over the whole islands of 

 the Indian Sea. Hence it is inferred that this general dis- 

 tribution of volcanic action is more likely to depend upon 

 one common cause, than to have its origin in a number of 

 local and detached causes. It is evident, however, that the 



