

REVIEW OF EVIDENCE 

 REGARDING THE PHYSICAL CON- 

 DITION OE THE EARTH. 



[fjcin^' e.\'lr<u:l from Address to I lie Mathematical <ind 

 rhysicttl Section of the British Association, (/'Arv;;< 

 September ;///, 1876.] 



Till; evidence of a high internal temperature is 

 too well known to need any quotation of particu- 

 lars at present. Suffice it to say that below the 

 uppermost ten metres stratum of rock or soil 

 sensibly affected by diurnal and annual variations 

 of temperature there is generally found a gradual 

 increase of temperature downards, approximating 

 roughly in ordinary localities to an average rate of 

 I " centigrade per thirty metres of descent, but much 

 iter in the neighbourhood of active volcanoes 

 and certain other special localities, of compara- 



