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. I have worked two days at one and spoiled it, principally from the want of steadiness." For Watt, it must be remembered, was now a very old man. He then proceeded to send Murdock the drawing of a "parallel motion for the machine," to be executed by the workmen at Soho. The truss braces and the crosses were to be executed of steel, according to the details he enclosed. "I have warmed up," he concludes, "an old idea, and can make a machine in which the pentagraph and the leading screw will all be contained in the beam, and the pattern and piece to be cut will remain at rest fixed upon a lath of cast iron or stout steel." Watt is very particular in all his details: "I am sorry," he says in one note, "to trouble you with so many things; but the alterations on this spindle and socket [he annexes a drawing] may wait your convenience." In a further note, Watt says. "The drawing for the parallel lathe is ready; but I have been sadly puzzled about the application of the leading screws to the cranes in the other. I think, however, I have now got the better of the difficulties, and made it more certain, as well as more simple, than it was. I have done an excellent head of John Hunter in hard white in shorter time than usual. I want to show it you before I repair it." At last Watt seems to have become satisfied: "The lathe," he says, "is very much improved, and you seem to have given the finishing blow to the roofed frame, which appears perfectly stiff. I had some hours' intense thinking upon the machine last night, and have made up my mind on it at last. The great difficulty was about the application of the band, but I have settled it to be much as at present."