near Peyiryn, and on the Mode of working it. 323 



is placed on edge, as it usually is when the vertical cleaving 

 has been first effected. The identity of these terms, in regard 

 to the direction of the cleaving, must be attended to in speak- 

 ing to stone-cutters; they refer only to the different positions 

 of the blocks of granite. The granite splits most easily on 

 this line, and its existence is strongly asserted to be found in 

 some varieties in which the " cleaving line " is not so strongly 

 marked : it is likewise notorious that it is found in elvan or 

 porphyry; so that a workman by attending to this point, con- 

 stantly gains more wages than others in breaking stones for 

 roads at tutwork*. It is readily known in the quarry ; but 

 some skill and practice is required to find it in separated 

 stones : 



2nd, Cleaving : 



The " cleaving line" is vertical, and is said by the stone- 

 cutters to be in the general direction of the crystals of felspar: 

 it is instantly pointed out by them, but is more readily seen 

 in coarse than in fine grit. Near Penryn it runs N.N.W. 

 and S.S.E., varying 15 or 20 degrees either way: it conse- 

 quently generally coincides with one of the vertical natural 

 joints, though in many instances it does not correspond, but 

 crosses them, often at an angle of 30 or 40 degrees. In these 

 cases it appears the cleaving line, or general direction of the 

 felspar crystal, keeps it in a N.N.W. and S.S.E. direction, and 

 the joints are " unconformable." Part of the Cornish parapet 

 of London Bridge was supplied from a rock which was split 

 up parallel to the joints, and diagonally across the cleaving 

 line, to prevent waste of stone. The appearance is exactly 

 similar to a common observer, though a practised cleaver 

 would probably point out every stone from that rock, certainly 

 if allowed to break the stone : 



3rd, The tough way, or across the grain : 



This is asserted by the stone-cutters to be a tran verse sec- 

 tion of the felspar crystals, and at right angles with the 

 cleaving line. 



The power required to effect a fracture on these lines is 

 very different, and has been estimated in the following pro- 

 portions: — 



1st. Capping or quartering =2 



2nd. Cleaving = 3 



3rd. The tough way « 5. 



In one trial of the tough way and capping way the power 

 used was estimated as follows : — 



* Tuiwovk is the term used in Cornwall to denote work contracted for 

 with the workmen by measure. — Edit. 



2T2 



