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II. On the Composition and Origin of the Waters of a Salt 

 Spring in Huel Seton Mine, with a Chemical and Microscopical 

 Examination of certain Rocks in its vicinihj. By J. Arthur 

 Phillips. M.Inst.C.E., F.G.S., F.C.S., $c* 



[With a Plate.J 



HUEL SETON Copper-mine is situated about one mile 

 north-east of the town of Camborne, Cornwall, and is 

 distant from the sea, on the north coast, a little more than three 

 miles. Its position will be readily understood by the aid of the 

 accompanying skeleton map (Plate I.) of the district, traced from 

 that of the Geological Survey. 



The workings of Huel Seton are entirely in " killas," or clay- 

 slate ; and the saline waters issue at the rate of 50 gallons per 

 minute, and at a temperature of 92° F., from the eastern fore- 

 breast of the 160-fathom level f. This has intersected a fault 

 or cross-course, which can be traced in a northerly direction to 

 the sea. The temperature of the level from the end of which 

 the water issues, like that of the water itself, is 92° F. 



Fig. 1, 



The lode ab,cd, fig. 1, 

 which is not well defined, and 

 is frequently a mere narrow 

 fissure in the clay-slate, has 

 been driven on to its point of 

 intersection b with the cross- 

 coursee/,andisbelievedtohave 

 been thrown in a southerly di- 

 rection from b to c. A dyke 

 of porphyry, G H, 40 feet in 

 w T idth, courses parallel with 

 the lode at a distance of a few 

 fathoms to the north ; but its 

 intersection with the cross- 

 course not having been seen, 

 it is not known whether any 

 throw or dislocation actually 

 takes place at this point, as 



* Communicated by the Author, having been read before the Royal 

 Society, January 30, 1873. 



f My attention was first directed to the discovery of this spring by Mr. 

 W. J. Henwood, F.R.S., of Penzance, who forwarded me in June last a 

 cutting from a local newspaper headed "A Salt Spring in Hr.el Seton 

 Mine." This notice states that the water had been sent to Mr. S. T. 

 Rowe, analyst to the Truro Agricultural Association, and that an analysis 

 had been returned " showing it to be highly impregnated with salt, salts of 

 lime, and other chemical matter to the extent of 1072 grains to the impe- 

 rial gallon." It then goes on to say, " very little iron, no copper, and no 



