104 Capt. W. Francis on the High Temperature 



strata, &c. ; and the water so discharged into the mines will 

 be found to be of lower temperature than the usual coming 

 stream. 



Having endeavoured to account for the difference in the 

 temperature of the water, I should be glad were I able to 

 advance some facts illustrative of the source of heat itself; 

 but although I have watched narrowly the various circum- 

 stances under which the highest temperatures have been ob- 

 served, I am still in some doubt as to the causes by which 

 they are produced. 



It is a commonly received notion that the highest degrees 

 of temperature are indications of large bodies of ores being 

 contiguous, if not actually open to sight ; but at the United 

 Mines, and in others also, the lodes in those levels where the 

 heat is greatest, are almost without ores, and both the lodes 

 the rock about them are hard and very compact. At the 

 same time I admit, that such lodes have been found, some- 

 where, to contain large quantities of copper ore ; but my ob- 

 ject in making the preceding remark is rather to shew that 

 the presence of great heat is not to be considered an infal- 

 lible indication of large masses of ores being near at hand. 



It should also be observed, that those lodes which yield 

 the most copper ores generally hold considerable quantities of 

 other minerals, such as iron-pyrites, arsenic, &c. ; and it be- 

 comes a question, whether these may not account for much, 

 if not the whole, of the heat in the mines. 



That most of the lodes, and especially those which have 

 yielded large quantities of copper ores, have, at some period, 

 been under the influence of great heat, there can be no doubt, 

 and to such an extent as to fuse their contents ; and I see no 

 reason for believing otherwise than that intense heat still 

 exists in them at a distance from where they have been pene- 

 trated: but it should be remembered that the symptoms 

 indicating the action of heat are not so frequent or strong in 

 the deepest parts of those mines which have been worked to 

 the greatest depths, as they are at higher levels, and espe- 

 cially near the surface, where gosson, at the depth of a few 

 fathoms, or even a few feet, usually exhibit this fact in the 

 clearest manner. I have had numerous opportunities of 



