46	ADAMAS.
	sedulously at this art, has left many curious details of the process as carried on in his times. He gives a figure of an ingenious con­trivance invented by himself for cutting several stones at once. It may be briefly described as a horizontal, circular frame, per­forated with holes, which received as many handles, on whose ends the diamonds were cemented.8 These handles, by weights applied above, kept the stones in close contact with the wheel revolving below horizontally, which was a mere rim of pewter equal in circumference (three feet) to the frame above, and pro­vided with a border to keep the diamond-dust and oil with which it was moistened from falling off. As may be supposed, from want of motive power, the operation was very slow : he mentions that it was only necessary to unbed each stone once a week. But it must be borne in mind no cutting of facets was as yet attempted : the wheel had only to attack the large and simple planes of tables and of pyramids. He knows nothing of the brutage or preliminary shaping of the stone, but states that this pewter wheel was employed for cutting down the diamond as well as for polishing it. The diamond-powder was then obtained by breaking up inferior stones with a large hammer: its value was ten thalers per scruple. He also notes that a perfect table-diamond then sold for fifty ducats, and he supplies a table con­structed after a somewhat complicated theory for ascertaining the value in proportion to the weight; but the result approximates pretty nearly to the modern, viz., to square the number of carats, and multiply the sum by the selling price of a stone of one carat. For example, supposing the latter to be 81. (as it is at present), the value of one of 5 carats" would be 5 x 5 = 25, which multiplied by 8 gives 200l (Barbot states the selling price of a perfect