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posed in. See the left hand lower figure. The right hana 

 geometrical figure shows the faces of the crystal, the top 

 and bottom being primitive, with which the fracture agrees. 

 This figure is about the size of a crystal, from the same 

 place, in the possession of R. C. Fergusson, esq. which has 

 the same colours as the other, though more dilute. This is 

 perhaps peculiar to the Scotch Topazes, as may be verified 

 hereafter ; for they may prove to be more common than is 

 now expected. The people that gather them, often call the 

 Cairn-Gorum Quartz by the name of Topaz (being a stamp 

 of value) ; and they are sold indiscriminately. This cry- 

 stal, which bears the marks of many a violent storm on its 

 worn edges, has been broken through the primitive base 

 transversely to the column, and is fractured in the laminae, 

 showing the order of the prismatic colours very well; and by 

 pressure these colours are spread wider, which shows that 

 there is a great degree of elasticity in the laminae. 



The geometrical figure is to show more distinctly the faces 

 that are in the principal figure, which is rather remarkable 

 for not having the faces so constantly opposite as they ge- 

 nerally are in Topazes. Between the large pentangular face 

 (n of Hauy) and the primitive apex, there is a parallel face, 

 not mentioned by Hauy, and perhaps one opposite, but so 

 small that, as the crystal is rounded by attrition, we are 

 not sure it is there. At the lower corner is the triangular 

 face (c of Hauy), on the nearest side, but I think not on the 

 opposite ; but it is marked in the outline to show where it 

 would come. The two faces on each acute side of the 

 prism are primitive, on the top of which a want of increase 

 forms two faces (o, o, of Hauy). 



The larger four sides of the prism are the faces (I ol 

 Hauy). The figure within the outline shows the position 

 of the primitive faces and fracture. The obtuse angle of 

 the base is 124° 22' according to Hauy. 



The value of Topazes depends much on their colour and 



