56 POPULAR LECTURES AND ADDRESSES. 



ance of investigation of underground temperature 

 was not denied by geologists, before whom the 

 subject was brought in the first instance, on that 

 occasion, by a paper by the Hungarian naturalist, 

 Schwarez. A result of the discussion which 

 followed the reading of that paper was the appoint- 

 ment of a committee l for investigating underground 

 temperature. 



27. The laws of the progress of summer heat 

 and winter cold downwards were investigated 

 thoroughly by the great French mathematician 

 Fourier, and made the subject of observation in 

 different localities. We know very well now what 

 temperature, so far as the annual variation is con- 

 cerned, may be expected to be found at ten, 

 twenty, or thirty feet down, according to the con- 

 ductivity and capacity for heat of the strata. If 

 we bore down to a depth of twenty-four feet we may 

 find, in mid-winter, the highest temperature. Prob- 



1 [Note of Jan. 4, 1893.] This Committee has been reappointed 

 from year to year ever since, and, under the persevering and able 

 guidance of Prof. Everett, continues to obtain and publish valuable 

 information regarding underground temperature in all parts of the 

 world. 



