46 COSMOS. 



Here a subterranean stratum of ice was pierced to a depth of 

 more than 382 feet. The thermometer was sunk at eleven 

 points along the lateral walls of the shaft, between the surface 

 and the greatest depth, which was reached in 1837. The 

 observer was obliged to be let down standing in a bucket, 

 with one arm fastened to a rope, while he read off the ther- 

 mometric scale. The series of observations, whose mean 

 error does not amount to more than 0-45 F., embrace the 

 interval between April, 1844, and June, 1846. The decrease 

 of cold was not proportional to the depth at individual points, 

 but nevertheless the following results were obtained for the 

 total increase of the mean tempera; ui'cs for the different 

 superimposed frozen strata : 



50 feet... ...17'13Fahr. 



100 



150 

 200 

 250 



382 



,20 0> 26 

 .2l-43 

 .23-27 

 .24 vt!) 

 .26-GO 



After a very careful consideration of all these observa- 

 tions, Middendorff determined the general increase of tem- 

 perature to be 1 F. for every space varying from 44-5 to 

 52 feet.* This result shows a more rapid increase of heat 



gin to continue the boring; and up to 1837, although an opening had 

 been made to a depth of 382 feet below the surface, it had not pene- 

 trated beyond the ice. 



* Middendorff, Rtise in Sib., bd. i., s. 125-133. "If we exclude," 

 says Middendorff, "those depths which did not quite reach 100 feet, 

 on the ground that they were influenced by annual deviations of tem- 

 perature, as was determined by experiments previously made in Si- 

 beria, we shall still find certain anomalies in the partial increase of 

 heat. Thus, for instance, between the depths of 150-200 feet the 

 temperature rises at a ratio of 1 F. for only 29*3 feet, while between 

 250-300 feet the corresponding increase is 96*4 feet. We may, there- 

 fore, venture to assert that the results of observations that have hith- 

 erto been obtained in Shergin's shaft are by no means sufficient to 

 determine with certainty the amount of the increase of temperature, 

 and that, notwithstanding the great variations which may depend upon 

 the different conductive powers of the terrestrial strata, and the dis- 

 turbing influence of the air or water which enters from above, an in- 

 crease of 1 F. occurs for every 44-52 feet. The result of 52 feet is 

 the mean of six partial increases of temperature, measured at intervals 

 of 50 feet between the depths of 100 and 382 feet. On comparing 

 th mean annual temperature of Jakutsk, 13'71 F., with that which 

 was found from observation to be the mean temperature of the ice 

 (2G-6) at the greatest depth of the mine (382 feet), I find 29-6 feet 

 for every increase of 1 F. A comparison of the, temperature at the 

 deepest 'part with that at a depth of 100 feet would give 4 1 '4 feet for 



