XIX. On a Shifted Vein occurring in Limestone, 



By J. Mac Culloch, m.d. f.l.s. President of the Geological Society, 

 Chemist to the Ordnance, Lecturer on Chemistry at the Royal 

 Military Academy, and Geologist to the Trigonometrical Survey. 



[Read November 15th, 1812.] 



X HE shifting of veins on a small scale is much more common 

 than the larger phenomena of this nature, which are neverthe- 

 less of frequent occurrence wherever veins exist. These larger 

 dislocations are known to arise either from the lateral motion or sub- 

 sidence of the containing parts, the sides of the line of fracture 

 sometimes remaining in contact, and being at others separated by 

 a vein of another description, too well known among miners to 

 need any comment here. I know not why mineralogists have some- 

 times imagined that such appearances were in the smaller examples 

 fallacious, and were contemporaneous with the formation of the 

 containing stone. The vein represented in the accompanying draw- 

 ings is at any rate too remarkable to admit of such an explanation, 

 and its character is sufficiently decided to establish a general rule 

 in favour of all similar appearances. 



The rock in which this shifted vein is contained is a secondary 

 limestone, and was brought from Ireland. The specimen, which 

 formed a mill-stone of six feet in diameter, belongs to the Royal 

 Powder Works at Waltham Abbey. 



