112 ^Proceedings of the Royal Physical Society. 



The theory of a Central Heat, or of a High Tem- 

 perature in the Interior of the Earth. The hypothesis 

 of a central heat is of ancient origin, and more or less con- 

 nected with the traditions of almost all nations. It assumes 

 that there exists within the earth a vast mass of incan- 

 descent fluid matter, the crust of which forms the habitable 

 part of our planet, and this hypothesis has played a pro- 

 minent part in many schemes of world-making that have 

 long since been forgotten. At the close of the last and 

 beginning of the present century, two rival schools of geology 

 sprung up under the names of Wernerian and Huttonian. 

 The founder of the first was the justly-celebrated German 

 philosopher, Werner, belonging to the University of 

 Freiberg. His leading doctrine was " that the order of 

 position which rocks maintain with respect to the centre 

 of the earth denotes the order of their formation, and 

 that the present arrangement of the rocky strata had 

 been chiefly effected by the action of water — the crystallis- 

 ing process being afterwards induced by certain chemical 

 affinities and molecular changes amongst the particles of 

 which they are composed." With Werner, geology as a 

 science may be said to have commenced — that is, as a 

 science founded upon observation and experiment derived 

 from a careful examination of the structure, contents, and 

 stratigraphical position of the rocks themselves. The second 

 school originated with Dr James Hutton, bom in Edin- 

 burgh in 1726, and may be termed the Edinburgh school of 

 geology. His well-known work on the " Theory of the 

 Earth" was published in 1795, the preparation of which is 

 said to have occupied his attention for a period of more 

 than thirty years. The Huttonian theory may be divided 

 into two branches or series of suppositions not necessarily 

 dependent upon each other. One branch of the theory 

 assumes that the strata constituting the crust of the earth 

 are, from the nature of their mineral structure and the con- 

 stant operation of the agents to which they are exposed, 

 liable to decay ; and that, by being worn down and trans- 

 ported to the sea, they furnish materials for new strata to 

 be formed and afterwards elevated ; and that from the 



