ON UNDERGROUND TEMPERATURE. 15 



favoured by the large dicametcr of the well (1-35 metre at the smallest), and 

 may have been further jjromoted by the same cause vehich stopped the works 

 and rendered tubing necessary — namely, caving in. 



Herr Johann Grimm, Director of the School of Mines at Przibram in 

 Bohemia, has furnished some valuable results from observations made by 

 himself in the year 1830, and again in 1854-55, in the deepest mines of 

 that district. 



The observations in 1830 showed a temperature 11°- 9 E. at a depth of 

 1127-4 Austrian feet, as against a temperature 7°-34 at 66 feet. The dif- 

 ference here is 4°-56 R. in 1061-4 Austrian feet, or 10°-26 Eahr. in 1100 

 English feet, which is at the rate of 1° Pahr. in 107 English feet. 



The observations in 1854-55 showed a temperature of 13°-08 R. at a 

 depth of 1832-3 Austrian feet, as against 7°-05 R. at 66 feet. The dif- 

 ference here is 6°-03 R. in 1766-3 Austrian feet— that is, 13°-57 Eahr. in 

 1832 English feet, which is at the rate of 1° Eahr. in 135 English feet. 



The following is a tabular statement of the results obtained at different 

 depths in the observations of 1854-55 : — 



Taking the differences of successive numbers in the last two columns, we 

 deduce the following rates of increase : — 



In the first 68 feet Unknown. 



In the next 231 „ 1° per 200 feet, 



322 „ 1° per 170 „ 



318 „ l°per 45 „ 



351 „ ...... Pper 700 „ 



124 „ 1° per 110 „ 



238 „ l°per 132 „ 



248 „ 1° per 1400 „ 



1900 



If we had omitted the last 248 feet from the reckoning, the average rate 

 of increase would have been 1° for 120 feet. 



The following explanatory remarks are extracted nearly verbatim from 

 Herr Grimm's letters : — 



" The depths of the shafts in these mines, and specially of the Adalbert 

 and Maria shafts, you can see from the annexed Table [Section annexed, 

 showing fifteen shafts]. The Adalbert shaft is sunk perpendicularly to the 

 depth of 470 Yienna fathoms = 891 -5 metres from the shaft-brace to the 

 bottom of the shaft. 



" I have to remark that, for the observations of the temperatures, such 



