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for his curious pieces of mechanism, who, in the me-moirs of the academy for the year 1757, lately printed,gives an account of his success, and of the establishment ofsuch a manufacture at Lyons.

The lower roll is made of wood, thirty-two inches inlength and fourteen in diameter; the upper one of copper,thirty-six inches long and eight in diameter : this last ishollow, and open at one end, for introducing iron heaters.For making the rolls cylindrical, he has a particular kindof lathe, wherein the cutting tool, which the most dex-trous hand could not guide in a streight line through sucha length as thirty-six inches, is made to slide, by means ofa screw, on two large steel rulers, perfectly streight, andcapable of being moved at pleasure, nearer, and alwaysexactly parallel, to the axis of the roll.

He first disposed the rolls nearly as in the commonslatting mill. In this disposition, ten men were scarcelysufficient for turning them with force enough to dulyextend the gilding; and the collars, in which the axesof the rolls turned at each end, wore or gulled so fast,that the pressure continually diminished, insomuch that apiece of stuff of ten ells had the gilding sensibly less ex-tended on the last part than on the first. He endeavouredto obviate this inconvenience by screwing the rolls closerand closer in proportion as the stuff passed through, or asthe wearing of the collars occasioned more play betweenthem ; but this method produced an imperfection in thestuff, every turn of the screw making a sensible bar acrossit. To lessen the attrition, each end of the axes, insteadof a collar, was made to turn between three iron cylin-ders called friction-wheels : but even this did not answerfully, for now another source of unequal pressure was dis-covered. The wooden roll, being compressible, had itsdiameter sensibly diminished : it likewise lost its round-

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