of Springs, and their Intensity at various Periods of the Year. 177 



But as the metalliferous veins, which have a direction of from 

 east to west, or thereabouts, suffer frequent intersections and 

 dislocations by the cross veins, they do not convey the liquid 

 to a very great distance in their longitudinal extent. But 

 the cross veins, which have a direction of about north and 

 south, are in many cases supposed to traverse the Cornish 

 peninsula from sea to sea, and although sometimes, are not 

 frequently, dislocated, and consequently may be the medium 

 through which sea-water may enter the mines. There are 

 some mines in which the water stands at the. adit, (North 

 Downs and Huel Busy,) which intervene between those in 

 which the muriate of soda was detected and the sea; but as 

 the latter are by far the deeper, it may be readily admitted 

 that the percolation may have taken place at or near the lowest 

 levels. But it has not yet been shown that sea-salt does not 

 exist in the water of North Downs and Huel Busy; and until 

 a long continued series of observations shall show its absence, 

 I think we may reasonably adopt Mr. Fox's suggestion. 



The level at which the water stands in some stopped mines 

 is not unworthy of notice. Poladras Downs is about a mile 

 north of Huel Vor ; before its working was resumed, the water 

 during the winter stood at the adit, but in summer it sunk be- 

 low that level, which is fourteen fathoms deep. Great Work 

 and Huel Breage are about a mile west of Poladras; in winter 

 the water runs out at the adit, but in summer it sinks three or 

 four fathoms; the adit is about thirty fathoms deep. These 

 facts have been communicated to me by G. S. Borlase, Esq. 

 F.R.S. In Huel Falmouth, before the resumption of opera- 

 tions, the water rose to the adit, twenty-five fathoms deep, in 

 winter; whilst in summer it sank about six or seven feet be- 

 neath it. 



I believe it may be assumed as a general fact, to which 

 there are not many exceptions, that, cateris paribus> mines 

 worked in the slate of Cornwall afford much more water than 

 those in granite. 



I believe my numbers do not coincide with Mr. Dalton's 

 on the same subject*; but through the kindness of John 

 Taylor, Esq. F.R.S., I am to be favoured with engine-reports 

 and other information from his mines in Mexico ; and if leisure 

 permit, I hope to submit them to calculation, as they may 

 assist in determining the question on which I feel compelled 

 to differ from such high authority. 



Perran Wharf, near Truro, W. J. H. 



January 28th, 1831. 



* Manchester Memoirs, O. S. v. p. 346. 

 N. S. Vol. 9. No. 51. Mar. 1831. 2 A XXXII. On 



