Page:A treatise on diamonds and precious stones including their history Natural and commercial.djvu/105

 tent of a brilliant, that the old rules for proportioning its dimensions are now nearly obsolete: the diamond-cutters have almost discarded the use of measures, and, in forming the facets, trust wholly to the eye. If, however, the brilliant were formed according to the rules, it would be in the best proportion, and exhibit the greatest possible refulgence. At present it is the practice in cutting a diamond almost exclusively to consider which form the rough stone is best calculated to produce, without any regard to scientific accuracy.

the octahedron is the most common form of rough diamonds, I will illustrate what Ihave to observe on the art of culling, by supposing such a diamond, which is technically called a six-cornered stone, to be given to a workman to make into a brilliant. The tabie and collet are cut upon opposite solid angles, in a direction perpendicular to the axis of the crystal, and the facets obliquely, upon the la-