102 Ctipt. W. Francis on the High Temperature 



ferent directions, might ultimately appear in some of our 

 mines, brought up, perhaps, in the largest proportions, by 

 the upward tendency of the more heated currents of water. 

 ■^-The Fourteenth Annual Feport of the Hoyal Cornwall Fo- 

 lytechnic Society, 1847. 



On the High Temperature of the Water at the United Mines, 

 By Captain "W. Francis. 



Whitehall, 2d September 1846. 



Dear Sir, — In fulfilment of my promise to you yesterday, 

 I now give you some facts which have come under my notice 

 relative to the temperature of water in our mines, especially 

 in reference to the great difference in the heat of water 

 issuing from different parts of the same level ; remarkable 

 instances of which are now observed in the United Mines. 



The United Mines on the south are traversed from west 

 to east throughout their whole extent by two large elvan 

 courses, which are of considerable thickness, and whose 

 direction is almost parallel with the principal lodes. At 

 the surface, the distance from the south lode to the first 

 elvan course is about 200 fathoms, and to the second about 

 230 fathoms. By the dip or underlie, northward, of the 

 elvan courses being so much faster than that of the lodes, 

 the former intersect and pass through the latter at depths 

 which vary in different parts of the mines ; but the 155 fa- 

 thom level may be taken as the average depth at which the 

 south lode passes through the first elvan course ; the middle 

 lode passes through it at the 170 fathom level ; and the 

 north lode at the 194 fathom level ; whilst the second elvan 

 course, as yet, has only been seen at the 220 fathom level, 

 where the south lode is in it, and the other two lodes can 

 only be intersected by it at a greater depth. These elvan 

 courses are distinctly traceable for several miles, and are so 

 jointed and open, especially near the surface, as to become 

 ready conductors of large quantities of water ; and to this 

 circumstance is to be mainly attributed the unusual quan- 

 tity of water which we have to contend .with in these mines, 



