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vations upon corundum ; namely, that this substance might 

 he nothing more than a dense variety of felspar. He soon 

 however entirely gave up this idea, after he had it in his 

 power to examine more particularly the nature of co- 

 rundum." 



Upon comparing the mechanical divisions of the corun- 

 dum of Ceylon with the Scotch one, we find that it is not 

 only parallel to the six faces of the rhomb, as described both 

 by Bournon and Haiiy, but also parallel to eight other faces, 

 all which are mentioned in Haiiy's description of his fel- 

 spath apyre, two of which are mentioned by him in his 

 Telesie, and the other six not mentioned any where as 

 existing in the corundum of Ceylon, but which we find in 

 some of our specimens. These faces are not so neat, or 

 so easily obtained, as those parallel to the rhomb. The 

 gangue is chiefly composed of a coarse granite intermixed 

 With indurated asbestos. 



Mr. Jameson mentions the corundum of Tirie; which 

 however must be very different from this, and he quotes 

 Mr.Greville's memoirs in Trans, of Royal Society for 1798, 

 page 40, who observes that it scratches glass readily, but not 

 rock crystal. Jameson says, u I believe there are specimens 

 of this corundum in the Museum of the University, and of 

 these I shall probably communicate an account in the close 

 of this volume:" but as he does not seem to say anything 

 more about it, we hope we shall have it settled in his work 

 now coming out. We presume that this is no more thought 

 of as a corundum, as C. Bournon in Phil. Trans. 1802 

 makes no mention of it as such : therefore ours is the only 

 thing known at present as a corundum from Scotland. 



