U Summaiy Revk-w of the late Investigations 



" In taking the temperature of the water in the difl'erent 

 levels of mine% care was generally observed to select the largest 

 streams, and to put the thermometer at or near the places where 

 they first flow into the mines, so that the influence of any heat 

 from the miners seems to be put out of the question." 



" It appears that in almost all the mines wliich have been 

 examined, the highest temperature has been found at the bot- 

 tom; and it is deserving of notice, that here, in most instances 

 that I have investigated since my last paper, very few Avork- 

 men are employed ; and generally their number increases at 

 each level in ascending from the bottom, as high up as one- 

 quarter or even one-diird of the way ; so that not very far 

 from the middle of mines they are frequently the most nu- 

 merous. At a level 180 fotlioms under the surface, in the 

 United Mines, I find the temperature of the water, which w;is, 

 and had been during twelve months, 30 fiuhoms deep in the 

 mine, was 80°, and a stream of water flowing into the same 

 level was 87°. This is only half a degree less than it was at 

 the same place in 1820. At that time, about 400 men were 

 employed in the mine 8 hours each day, and about 50 on 

 an average for the remainder of the 24 hours. When the 

 last observation was made, only about 200 men worked in the 

 mine 8 hours a day, and about 50 during the remaining 16 

 hours." 



" I do not dispute, that in close levels, where there is no cur- 

 rent, the presence of the men increases the temperature of the 

 air ; yet it does not appear by the above table tliat the heat of 

 the air is usually much greater than that of the water in the 

 same places, — perhaps on an average not exceeding 1° or 2°. 

 In niany instances, indeed, the water was from 1° to 4° warmer 

 than the surrounding air, and this occurred in several mines 

 at or near the deepest levels." 



" Before I conclude my enumeration of facts, it may per- 

 haps be desirable to state the temperature of tlie Avater which 

 flows through the great adit, and is discharged near Nangiles 

 mine, above Carnon Valley. This adit traverses the }irin- 

 cipal mining district of Cornwall, and extends neai'ly 30 miles, 

 including its different ramifications, and more than 5 miles 

 from one extremity to the other in one direction, and 3 miles 

 in another. The temperature of the water was taken near the 

 mouth of the adh about six weeks since, and was found to be 

 69*25°. Richard Thomas, land surveyor, of Falm.outh, 

 (author of an interesting map of a large jiortion of our mining 

 district,) has ascertained by frequent observations, that the 

 quantity of water discharged by the adit, at different times of 

 the year, has varied from 910 to 1644 cubic feet per minute: 



but 



