Observations on Sul terraneous Heat. 325 



5th, In the fifth gallery, the thermometer, plunged into a 

 water-tank near the great pit, rose to, — Temperature 17 J . 

 Depth 160™. 



6th, At the extremity of the gallery No. 9-f> a great quan- 

 tity of water is seen to issue from the roek slightly vitriolic : 

 the thermometer, when held a quarter of an hour in the midst 

 of the jet, constantly marked, — Temperature 19'7°* Depth 

 230 m . 



7th, When held in the air on one side, it also marked, — 

 Temperature 19*7°. Depth 230 m . 



8th, About 60 paces nearer the mouth of the pits, the 

 water of the stream formed from the above jet stood also 

 at, — Temperature 19-7°. Depth 230*. 



The bottom of the mine was under water which was 16 

 metres deep. I descended through a small pit, a short way 

 from the great one, to the level of the subterraneous lake. 



9th, The thermometer, when kept for a quarter of an 

 hour upon a plank floating in the water, marked, — Tem- 

 perature 18*8°. Depth 238 m . 



10th, When plunged in water it also indicated, — Tem- 

 perature 18*8°. Depth 238 m . 



All the water which flowed into this southern part of the 

 mine proceeded to the subterraneous lake from which it was 

 pumped up. 



11th, The temperatuft? of the water poured into the gal- 

 lery No. 7, from the pump, was, — Temperature 19*4°. 

 Depth 180 m . 



Proceeding along this gallery the water flowed into 

 another pit in the northern part of the mine. 



12th, Here it mingled with a small quantity of water, 

 the temperature of which was i^°. Depth J20 m . 



13th, And when the whole together were poured, by means 

 of pumps, into the uppermost gallery, they marked, — Tem- 

 perature 18*4°. 



We have here two classes of observations, which must be 

 kept distinct ; namely, those made in the northern, and 

 in the southern part of the mine. 



The former, in my opinion, indicate the natural tempera- 

 ture of the soil. No. 1, being made 20 ^L^O metres below 



X 3 the 



