PROFESSOR W. THOMSON ON THE SECULAR COOLING OF THE EARTH. 169 



fessor James Thomson.* The results which must follow from this tendency 

 seem sufficiently great and various to account for all that we see at present, and 

 all that we learn from geological investigation, of earthquakes, of upheavals and 

 subsidences of solid, and of eruptions of melted rock. 



33. These conclusions, drawn solely from a consideration of the necessary 

 order of cooling and consolidation, according to Bischof's result as to the relative 

 specific gravities of solid and of melted rock, are in perfect accordance with what 

 I have recently demonstrated! regarding the present condition of the earth's 

 interior, — that it is not, as commonly supposed, all liquid within a thin solid 

 crust of from 30 to 100 miles thick, but that it is on the whole more rigid certainly 

 than a continuous solid globe of glass of the same diameter, and probably than 

 one of steel. 



* Proceedings of the Royal Society of London 1861, "On Crystallization and Liquefaction as 

 influenced by Stresses tending to Change of Form in Crystals." 



I In a paper " On the Rigidity of the Earth," communicated to the Royal Society a few days 

 ago. April 1862. 



VOL, XXill. PART I. 



