RY WM, FKYAE, INSPECTOR OF BnXES, QUEEXSLAXD. 25 



the first 100 fathoms. That is, omittmg the temperature of 

 water pumped out of the mine and the thermal springs which 

 rise to the surface — a remarkable proof that the causes of 

 increase are local and exceptional, and not general — as arising 

 from any central body of fire. 



It is also stated that " the different metals or metalliferous 

 minerals indicate different ratios of increase of temperature. 

 Gold and silver, which are generally worked in mountainous 

 regions and between the tropics, showing 1 deg. to 30 fathoms, 

 while the inferior metals, lead, copper, and tin, worked on lower 

 levels, gave 1 deg. for each 8-9 fathoms." But Gympie is 

 neither within the trojjics nor in mountainous country, and yet 

 shews a lower ratio of increase than is here given. 



Again, taking the depth, irrespective of any other consider- 

 ation, the heat increased from the surface to 150 fathoms at the 

 rate of 1 deg. for 21-4 fathoms, but in the next 50, at the rate 

 of 1 deg. for 5 fathoms, and in the next 72, at the rate of 1 deg. 

 for each 60 fathoms. 



A very striking fact is, that the increase of heat "the ratio 

 in Avhich the temperature augments in descending is greater in 

 shallow than in deep mines." One set of 177 observations, not 

 in the deepest mines of Cornwall and Devon, exhibit increments 

 of temperature equal to 10 degs. each at intervals of about -47, 

 79, and 125 fathoms of descent, whilst 53 experiments in the 

 deepest levels or accessible parts of mines show the rock, water, 

 and air to preserve in round numbers a temperature of CO degs. 

 at 59 fathoms, 70 degs. at 132 fathoms, and 80 degs. at 289 

 fathoms, being an mcrease of 10 degs. above the mean temper- 

 ature of the surface at 59 fathoms ; this, however, would 

 apparently accrue in 42-4 fathoms, as Henwood has invariably 

 taken the plane of equal temperature as at 16-6 fathoms. An 

 additional 10 degs. for the liext 73 fathoms, and a third 10 degs. 

 for the next 107 fathoms ; thus showing, if not a cooling in des- 

 cent, at any rate a very great failing off from the ratio of increase 

 at the higher levels : a proof rather that the heat proceeds from 

 the surface than from the centre of the earth. 



D. C. Davies, F.G.S., &c,, &c., in his "Metalliferous Mines 

 and Minerals," says : — " Still, there are the facts that the air in a 



