450 Prof. Phillips on Subterranean Temperature. 



made arrangements for repealing this interesting experiment, 

 under different conditions, I shall not further anticipate the 

 account, which I hope he will soon publish, of the result of 

 his labours. 



10. The temperature of the water collected in the pit bot- 

 tom was 67°. The barometric observations were : 



B.P. Att.Th. Det. Th. 

 At the top .... at 11 a.m. 30*518 53° *9°1 It is a boiled 

 At the bottom at 1 1 a.m. 32-280 58 62 Vtube absolutely 

 At the top .... at 3 p.m. 30*518 58 49 J free from air. 

 Capacity of instrument ^y* 



11. On these results I beg leave to offer a few remarks. 

 The temperature of surfaces of rock exposed in subter- 

 ranean situations is subject to several modifying causes. 



1. The real interior temperature of the mass ; 



2. The local influence of external heating agents, which 

 are, respiration of workmen, lights, explosions, and fric- 

 tion ; 



3. The variable influence of the air which is made to cir- 

 culate through the passages of the works. 



12. It is evident that the most satisfactory experiments are 

 those in which the local and variable influences are the least 

 possible, or else the most easily ascertainable : they cannot be 

 wholly annihilated. In the present instance the small extent 

 of the underground workings is very favourable ; they are, in 

 fact, only just commenced; no horses are yet let down into 

 the pit; the extrication of gas from the fresh coal is so abun- 

 dant as to compel the use of the Davy-lamp, and to require 

 a very powerful ventilation. It is a circumstance too im- 

 portant to be overlooked, that the total influence of the ex- 

 ternal agents on temperature is the resultant of the heating 

 and cooling agency of the men, lights, currents of fresh air, 

 &c. If this total influence, in any part of the mine, be to aug- 

 ment the temperature of the surfaces, the interior parts will 

 be found colder than the surface, and the contrary. 



Now in the present instance, it was found that the resultant 

 of the external influences on the surface of the coal was 

 powerfully refrigerating ; for in those parts which were con- 

 tinually and had been long exposed to them, the surface tem- 

 perature was either the same or a few degrees above that of 

 the air ; in the parts which had been less exposed, this tem- 

 perature was higher: when fresh surfaces were exposed it 

 was highest of all, being 9° 6' above that of the air current. 

 As the workings proceed this great difference will probably 

 diminish, and then it may be not possible so clearly to prove 



