S4t2 Prof. Bischoff" on the Temperninre of 



workmen, were as mucli as possible avoided. They were always; 

 placed in the solid rock, and in spots above which there were 

 no halvens or other heaps of rubbish. The holes were bored in 

 such a manner, that the bulbs of the thermometer should lie at 

 least 40 inches below the surface of the rock, and only such were 

 used as were free from wet. 



During his observations on the hourly variations of the mag- 

 net, Reich had an opportunity of observing the rapidity with 

 which the air operates upon the rock even at a distance of 40 

 inches. The air in the mine shewed 48°.6 with but slight variations, 

 and a thermometer sunk into the rock 48°.(54 ; but when, after 

 44 hours' observation of the magnet, the temperature of the air 

 had been raised by the presence of the observers, and their two 

 candles, to 49°.'7, the thermometer in the rock, which was sulv- 

 ject to no change of air whatsoever, was found to have risen to 

 48°.71, 48". 73. This discovery destroyed all hope of obtaining 

 the temperature of the rock, quite free from the influence of the 

 air, by sinking the thermometers even 40 inches deep into the 

 rock. In order to ascertain whether the temperature of the 

 rock was raised or depressed by the air, at different points near 

 the scale of the thermometer sunk into the rock, were placed 

 others exactly corresponding with it. Thus, if the mean tem- 

 ])erature should be higher than that of the rock, it might be 

 concluded that the air tended to raise the temperature of the 

 rock ; and if lower, that it caused a depression. They were, 

 however, satisfied with knowing, whether an increase or decrease 

 took place, without determining to what extent it was carried. 

 The observations frequently led to no results. The thermo- 

 meters near the surface were generally observed three times 

 a-week ; those situated further down, twice. Reich estimates 

 the ei-rors of observation in some cases at 0.18. 



Another observation, v.hich proves how deep in the earth a 

 change of temperature in the neighbourhood, although small, if 

 it be but of long duration, may be felt, is worthy of notice, as 

 it shews how many unknown, as well as known circumstances, 

 may have influenced former thermometrical observations in 

 mines, and how little the want of concord in the results obtained 

 from them is to be wondered at. In tl^e mine of Beschert 

 GliicJc, in the Fretjberg district, a thermometer buried in the 



