OX UXDEKGKOUXD TEMPERATURE. 



l'Jj 



of the observations in the tabic, as being vitiated by the presence of pyrites 

 or by currents of air. 



All the galleries mentioned in the tabic arc classified according to the 

 sbaits with which they arc connected, and there are, tor the most part, six 

 of these galleries to each shaft. In the final reductions, Dr. Schwartz com- 

 pares the temperature in the deepest gallery of each shaft with the assumed 

 liican annual temperature of the ground at the shaft-mouth. For determining 

 this latter element the following data are employed. 



The mean temperature of the air at the School of Mines, fiorn twenty 

 years' observation, is 7°-2 C, at the height of 012-6 metres above sea-level. 

 The shaft-mouths arc at heights of from 498 to 703 metres above sea-level ; 

 and it is assumed that the temperature of the air falls 1° C. for 100 mctus 

 of elevation. It is further assumed that the mean temperature one met] c 

 deep in the soil is, in these particular localities, 1° C. higher than the mean 

 temperature of the air. The reasons given for this last assumption may be 

 thus summarized : — 



(1) Observations in various localities show that in sandy soils the excess 

 in question amounts, on the average, to about half a degree Centigrade. 



(2) In this locality, the surfaco is a compact rock, which is highly 

 heated by the sun in summer, aud is protected from radiation by a covering 

 of snow in winter ; and the conformation of the hills in the neighbourhood is 

 such as to give protection against the prevailing winds. Hence the excess is 

 probably greater here than in most places, and may fairly bo assumed to be 

 double of the above average. 



Omitting one shaft (Franz shaft), in which, owing to tho presence of 

 pyrites, the temperatures are abnormal, the following arc the principal re- 

 sults : — 



The best mode of combining the results from these five shafts is indicated 

 in the last line of the above Table, where the sum of the depths is compared 

 with the sum of the increments of temperature. We have thus a total in- 

 crease of 38°*3 C. in 1587 m., which is at the rate of 1° C. in 41-4 metres, 

 or 1° F. in 7~>-"> feet. 



As these results depend on an assumption regarding the surface tempera- 

 ture, it seems desirable to check them by a comparison of actual observa- 

 tions, namely, by comparing the deepest with the shallowest observation in 

 each mine. We thus obtain the following results : — 



o2 



