THE 



LONDON and EDINBURGH 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[THIRD SERIES.] 



MAY 1833. 



LI I. Some Remarks on the Granite found near Penryn, a fid on 

 the Mode of working it. By John S. Enys, Esq.*. 



'T^HE chief intention of this paper is to give publicity to the 

 ■*■ opinions of the persons employed in the supply of granite 

 shipped at Penryn, and to explain the mode of procuring the 

 rectangular blocks of granite which are used in the construc- 

 tion of large bridges, docks, &c. &c. This hard and compact 

 granite appears to run in parallel ranges through a coarser 

 and softer variety, forming together a granitic district north- 

 west of Penryn, of nearly a circular form, 7 or 8 miles in 

 diameter. One of these ranges is situated on the northern 

 side of the district: another near Penryn on the southern 

 limits. The latter runs N.E. and S.W., and is about 5 miles 

 long and from 1 to 1^ wide; it is marked throughout by large 

 loose rocks on the surface, from whence for many years the 

 quantity exported was obtained. An immense supply from this 

 source is still obtainable; but about five or six years since a se- 

 cond bed was found under some of the larger rocks, and this 

 in several places has been worked in quarries, locally termed 

 " bals ": these workings are so numerous as to afford strong 

 proof of a continuous range of hard granite. The stone is 

 found more free from stains in depth than at the surface, though 

 the supply is too abundant to require the workings to be car- 

 ried in any instance to a depth exceeding 14- or 15 feet. 



To prevent any misunderstanding, it may be advisable to 

 explain in what sense several words will be used. Rock will 

 mean either a solid mass contained between the natural joints 



* Communicated by the Author. 

 Third Series. Vol. 2. No. 1 1 . May 1833 2 T 



