Made of Lancaster. 55 



The two last species, together with the rujiventris and 

 ahdominalis^ are so nearly alhed, that they might with 

 propriety form a subdivision of the third group. 



ART. v.— AN ACCOUNT OF THE CHIASTOLITE OR 

 MACLE OF LANCASTER, By Charles T. Jackson, M. D. 

 Read April 2, 1834. 



Among the singular forms assumed by crystals^ none, 

 perhaps, are more curious than those of the mineral 

 called Chiastolite, or Macle. This mineral occurs 

 abundantly in the town of Lancaster; upon an eminence 

 called George HilL It is imbedded in clay slate passing 



into mica slate. The whole mountain is composed of 

 clay slate, but only a bed, of about ten feet in thickness, is 

 charged with the Blade. This bed may be examined upon 

 the road side, where the boundary line divides the towns 

 of Sterling and Lancaster. Besides this bed of MadeSy 

 there exists an immense abundance of erratic blocks or 

 boulder-stones which are scattered in great profusion 

 upon the south east side of the hill, none being found on 

 the north west. This fact I consider of value in geology, 

 as it concurs with so many others, to prove, that at some 

 period since the creation, there has been a powerful cur- 

 rent of water rushing over our continent from the north 

 west towards the south east : — a current of such mighty 

 power as to carry away with it enormous quantities of 

 large, rounded boulders, and deposit them many miles 



nal localities. It is highly probable that 



this w^as effected by that last grand cataclysm which 



overwhelmed the world, and to which the traditions and 



religious belief of every nation give ample testimony. 



The curious and beautiful forms of these cr}^stals cannot 



