PHYSICS OF THE GLOBE. 93 



two junctions were exposed to different temperatures; and 

 by regulating the temperature of the outer junction until a 

 galvanometer indicated no current, that of the buried junc- 

 tion would be known. This is essentially the method em- 

 ployed by Becquerel for many years past. {Nature, vol. 

 xviii., p. 505.) 



Sir William Thomson {Philosophical Magazine, May, 1878, 

 p. 370) proposes several problems regarding the conduction 

 of heat through rock, the principal of which is this : "A fire 

 is lighted on a small portion of an uninterrupted plane boun- 

 dary of a mass of rock, of the precise quality of that of Cal- 

 ton Hill, and after burning a certain time, is removed, the 

 whole plane area of rock being then freely exposed to the at- 

 mosphere. It is required to determine the consequent con- 

 duction of heat through the interior." The mathematical 

 discussion leads him to a series of conclusions which may be 

 found stated at length in the American Journal of Science 

 and Arts, III., xvi., p. 132. 



The temperatures in the St. Gothard Tunnel have been ac- 

 curately observed by the engineers, and their observations 

 discussed by Stapff and Hann. They, however, can give little 

 or no reliable information as to the temperature of the earth 

 in its interior, and the whole of our present knowledge on 

 this subject is thoroughly unsatisfactory. 



Mr. William Morris, of Earl's Hill Colliery, publishes an 

 earnest remonstrance against accepting temperatures of the 

 ground as observed in coal-mines, as having anything to do 

 with the temperature of the earth at that depth. Such fig- 

 ures, according to him, are wholly dependent on the ventila- 

 tion of the mine. 



The temperatures of the spring-waters for two different 

 springs in Tokio, Japan, are given, apparently by Knipping, 

 in the last number of the Mittheilungen of the German-Asiatic 

 Society for each month of the years 1873 to 1877, and from 

 these he deduces a table for the correction to reduce any 

 month to the mean of the year. These corrections he has 

 then applied to observations of springs in other portions of 

 Japan, from which he deduces the mean temperature for the 

 year. 



The influence of artificial coverings and of shade upon the 

 temperature and moisture of the soil form the subject of a 



