The fitting the drills into the spindle by a taper of 1 in 6 will do.

They are perfectly stiff and will not unscrew easily.

Four guide-pullies answer, but there must be a pair for the other end, and to work with a single hand, for the returning part is always cut upon some part or other of the frame." These letters are written sometimes in the morning, sometimes at noon, sometimes at night.

There was a great deal of correspondence about "pullies," which did not seem to answer at first.

"I have made the tablets," said Watt on one occasion, "slide more easily, and can counterbalance any part of their weight which may be necessary; but the first thing to try is the solidity of the machine, which cannot be done till the pullies are mounted." Then again: "The bust-making must be given up until we get a more solid frame.