416 On the Temperature of Mines in Cornwall. [June , 



as regards the presence of miners. The adventurers of the above 

 united Mines still keep the engine (a water wheel) of Wheal 

 Trenoweth working for the purpose of reheving the burden of 

 their own engines. 



The adit at which the water is discharged is 32 fathoms from 

 the surface : here the water from Wheal Trenoweth 1 00 fathoms 

 from where it was drawn up was 54°. This water gradually 

 increased in temperature from this place, where we descended^ 

 to the mouth of the pump, where the water drawn from the 

 bottom was 56° : 15 fathoms deeper the walls of the shaft were 

 64° ; a gallery at this level 40 fathoms east of the shaft was only 

 63° ; and five fathoms deeper still, or 52 from the surface where 

 there is a second cistern of water, the water was 57° ; the walls 

 at the same time 54^°, and at the bottom QQ fathoms, or 396 

 feet, the water that ran through a small crevice, as well as the 

 vralls of the shaft, were still 54°. The temperature at the sur- 

 face before descent was 62° ; on our return 64°. 



Here I would say that there is positive proof of no increase of 

 temperature for 34 fathoms, being precisely the same at the 

 bottom as at the adit level. 



The increase of heat in the water at the cistern, and at the 

 mouth of the pump, I can only attribute to the friction of the 

 machinery, which certainly appeared to be very great at the 

 time. 



To show the influence of a few persons on the temperature of 

 the air of a small mine, I found on our return (being three per- 

 sons) that the air was 1° warmer than at our descent at the adit 

 level. 



Possibly I might be mistaken should I assert that the internal 

 strata of the earth generally are not warmer than the mean of 

 the surface. I do not find that 53° is at all too high for this 

 mean, and should we be able to find a single instance at the 

 bottom of some of our deep mines where the temperature is not 

 above the mean, I conceive Mr. P'ox's theory must be relin- 

 quished. 



Some of my experiments were made several years since, and, 

 perhaps, not with that degree of accuracy with which they ought 

 to have been. I have, therefore, refrained from giving them at 

 present. The above may be relied on. I mean to prosecute this 

 subject further ; and that by various means, particularly by sink- 

 ing a self-registering thermometer to the bottom of some of our 

 oldest and deepest mines long ceased working, and consequently 

 full of water. 1 think this the only certain means of arriving at the 

 wished-for accuracy. The facts when collected I shall certainly 

 present to the public. 



I am, Sir, your humble servant, 



M. P.MOYLE. 



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