On Underground Temperatures. Table 7. 



59 



11 



12 



13 



14 

 15 

 16 



M 



18 



19 



20 



Depths 

 below 

 surface. 



Feet. 



246 



412 



489 



230 



459 



781 



200 



558 



886 

 1246 



480 



504 

 900 

 1200 

 500—550 



600- 

 700- 

 800- 

 900- 

 1150- 

 1260- 

 1350- 

 240- 

 540- 

 720- 

 1140- 

 1320- 

 13S0- 

 6- 

 180- 

 480- 

 600- 

 600- 

 720- 

 780- 



-650 



-750 



-850 



-950 



-1260 



-1350 



-1400 



-300 



-600 



-780 



•1200 



-1380 



-1440 



-60 



-240 



-540 



-660 



-720 



-780 



-840 



YI 



Tempera- 

 ture at 

 depths. 



Fahr. 



53 -5 C 



56 



58 



54 



62-5 



66 



55 

 59 

 66 

 60 



60 



68 



74 



65 



63 

 65 

 66 



71(a) 

 71 

 74 

 79 



58 1 



59 0) I 



63 I 



64 (a) f 

 78f i 

 82 J 



52 

 61 



63 

 64 1 

 66 



7o I 

 69 (a) J 



VII 



^References and Bemaeks. 



Daubuisson, "Journal des Mines," vol. xxi. p. 119 

 (1807). 



(a) Temperature of St. Brieuc. 



De Trebra, 1805-7, " Inn. des Mines," vol. i, p. 377 

 (1816), and vol. iii, p. 59. Obs. made in glazed 

 niches in rock. The mean of 2 years' obs. No 

 working going on. 



E. Bald, "Phil. Jour.," vol. i, p. 135 (1819). 48*5° 

 is the temperature of Cockermouth. 



Dr. Forbes, " Temperature of Mines," " Trans. Boy. 

 Soc. Cornwall," vol. ii, p. 159 (1820). Average of 

 observations made in six mines. Gives the tem- 

 perature of the air and water. These are the 

 water temperatures. 



(a) Here there was a strong current of air. 



B. W. Fox, " Trans. Boy. Soc. Cornwall," vol. ii, 



p. 19 (1820). 

 (a) Here there were strong currents of air. Obs. 



in rock, except the last, which was in water. 



Ibid. 



All these are water temperatures, 

 (a) Here the temperature of tbe air in gallery was 

 72°. 



hat the mean surface temperature of Cornwall was under 51°, and possibly even 

 "ss than 50°. This will account for the apparent discrepancy between the gradients 

 f many of the original observers and those given in the Tables II, III, IV. 



f A subsequent observation (No. 73) of Mr. Fox, made a year later, at the 

 epth of 1380 feet, gave a rather lower reading. A thermometer 4 feet long 

 was placed in a hole 3 feet deep, at a spot where no workmen were employed, 

 nd where the current of air was small. The hole was filled with clay round the 

 'em of thermometer, which was left in that situation for eighteen months, and was 

 ~und always to indicate a temperature of 76° or 76^°. In the experiment of 1820 

 he thermometer was buried in the rock to the depth of 6 or 8 inches, and filled 



und with earth. 



