44 INTERNAL HEAT OF THE EARTH, 



principally on climatic relations), the accurate determina- 

 tion of the temperature of the soil, and the thickness of the 

 subterranean Or ground-ice. He accordingly examined the 

 latter questions by means of borings and excavations from 

 21 to 61 feet deep, at more than twelve points (at Turu- 

 chansk, on the lenisei, and on the Lena), at distances of 

 from 1600 to 2000 geographical miles apart. 



The most important point, however, for geothermic obser- 

 vations, was the Schergin Shaft( 45 ) at lakutzk (lat. 62 2'), 

 where the subterranean icy stratum has been pierced for a 

 thickness of more than 382 English feet. Thermometers 

 have been inserted in the side walls of the shaft, at 

 eleven points situated vertically in respect to each other, 

 between the surface of the earth and the deepest part of 

 the shaft reached in 1837. The observer, in descend- 

 ing, had to read the thermometer scales standing in a 

 bucket, and holding by one hand to the rope. The series 

 of observations, of which the mean error is estimated at only 

 0'25 Cent., or 0*45 Pahr., extended over the interval 

 from April 1844 to June 1846. The decrease of cold was 

 not indeed always in proportion to the depth at each of the 

 separate points, but on the average the increase of tempera- 

 ture with increasing depth was found as follows : 



Engrl. Feet. Reaumur. Fahrenheit, 



o o 



50 .... -6-61 .... 17-13 



100 .... -5-22 .... 20-25 



150 .... -4-64 .... 21-56 



200 .... -3-88 .... 23-27 



250 .... -3-34 .... 24-49 



382 . . -2-40 26-60 



