DY W-AI. FKYAE, INSPECTOR OF MIXES, QUEENSLAND. 23 



.surface of -wliieli is 3,(jo0 feet above the Pacific and 1,750 above 

 the pUiin, from which it appears that by an observation taken at 

 4G fathoms' depth the temperature of the air was GtJ degs. ; at 127 

 fathoms it was 06'75 degs. and at 150 fathoms it was 0(j degs ; 

 thus shoAving that in this case at any rate there was practically 

 no change in more than 100 fathoms. All the observations were 

 made in the limestone formation, and a note is added to say that 

 the last mentioned observation, made at the bottom of the shaft 

 where the draft was very great, ought perhaps to be excluded from 

 the general average. But only the same quantity of air could pass 

 the bottom of the shaft that circulated through it, and of all 

 places tliat would be the least likely to be smaller in section than 

 the other portions. The fact that the temperature can be kept 

 down by a heavy draft is however an important conclusion, and 

 as the air rapidly assimilates to the temperature of the adjacent 

 rocks, it may be assured that there was practically no difference 

 of their temperature down to that point. 



In July, 1863, in the mine at ]\Iorro Velho, the temperature 

 of the water issuing from the hanging wall of the metalliferous 

 deposit, that is, from the rock above the lode which is generally 

 inclined somewhat from the vertical, at 28-o fathoms was 64*5 

 degs., while the water collected at the bottom of the engine shaft, 

 160 fathoms down, was 65 degs., showing a difference of half a 

 degree of temperature in 131-5 fathoms. 



Similar irregularities occur in the observations made in 

 Cornwall. Thus at Wheal ]\Iary Ann, j\Ienheniot district, a 

 large stream of water from a lode at the bottom of the mine, 98 

 fathoms deep, on 0th September, 1851, showed a temperature 

 of 67"5 ; but on 29th July, 1867, the water pumped to the 

 surface from a depth of 280 fathoms, showed 64-5, or 3 degs. less 

 temperature, although coming from 182 fathoms deeper. It may 

 have lost some of its heat hoAvever in the course of its transit 

 through the column of pumps. 



At Wheal Trelawny a small stream flowing out of the lode 

 8th September, 1851, at 95 fathoms deep stood at <6o degs. ; and 

 in July, 1867, water pumped to the surface from 210 fathoms 

 was 65-3 — that is, -3 of a deg. for 115 fathoms. It is noticeable 

 that in estimating the increase of temperature in depth, the 



