292 -Miner alogical Journey. 



m 



occurs in this town. It is situated about half a mile west of the pub- 

 lic house, upon the western declivity of a granite hill, which lies di- 

 rectly upon the public road. The Beryls occupy a vein a few feet 

 in width, and ten or twelve in length. In dimensions, they vary from 

 one, to two or three inches in diameter; but the closely aggregated 

 manner in which ihey occur, is not very favorable to a high degree 

 of finish in their form. Crystals that are tolerably complete, may 

 how^ever, be obtained, and occasionally, those with polished, terminal 

 faces J but we find them, more generally, with faces very unequally 

 produced j as, with two lateral faces very widely extended and im- 

 parting a tabular appearance to the crystal, or with four planes so en- 

 larged as to give a rhomboidal aspect, or finally, with the alter- 

 nate faces protracted in such a manner as to form a trihedral prism 



The most interesting circumstance connected with these crystals, 

 however, is their color, which varies from a delicate bluish green to a 

 white ; those of the first mentioned shade, possessing the ordinary 

 transparency of the species, while those of the latter are only trans- 

 lucent on the edges. The vein stone is quartz, slightly brown, with an 

 occasional intermixture of imperfectly formed feldspar crystals. 

 The longer crystals of Beryl offer the same peculiarity as respects 

 the fractures and reunion of the laminae at right angles to their axes, 

 as were noticed in the large Beryls of Acworth.* The devia- 

 ion from a straight line which the axis suffers, in consequence of this 

 disturbance, amounts in some instances to 5 or 10^ ; and the quartz 

 which penetrates between the joints, is in layers of half an inch in 

 thickness- In addition to this peculiarity, we observe here, also, a 

 slight curvature in some of the crystals, unattended by any fracture 

 in the prism. These observations I am induced to make with the 

 more particularity, since they appear to me important in the consid- 

 eration of the much agitated question among geologists, respecting the 

 origin of granite. With a celebrated writer upon geology, I am per- 

 suaded, "that much light must, at some period, inevitably be thrown 

 on the greater geological phenomena, by considering the chemical and 

 mechanical relations existing among the smaller portions which con- 

 stitute them J and that the language of Nature is often as intelligibly 

 spoken in the minute space of an Inch, as ui the immensity of a moun- 



tain. 



"* 



» 



A large joint of the Acworth crystal, in the possession of my fellow traveller 



Dr. Heermarm, illustrates these fractures in a very interesting manner. 

 * Ti^Bsactions of the Geological Society, Vol. II. p. 433. 



