Watt was, on his part, rather opposed to making further concessions, which only seemed to have the effect of inviting demands for more.
“People,” said he, “do not employ us out of personal regard, but to serve themselves; and why should not we look after ourselves in like manner.... John Taylor died the other day worth 200,000l., without ever doing one generous action. I do not mean that we should follow his example. I should not consent to oppression or to take any unfair advantage of my neighbour’s necessity, but I think it blameable to exercise generosity towards men who display none towards us. It is playing an unfair game when the advantage is wholly on their side. If Wheal Virgin threatened to stop unless we abated one-half, they should stop for me; but if it appeared that, according to the mode settled in making the agreement, we had too high a premium, I should voluntarily reduce it to whatever was just.”
While Boulton was fighting for dues in Cornwall, and labouring as before to improve the business management of the mines in which he was interested as a shareholder, Watt was busily occupied at Soho in turning out new engines for various purposes, as well as in perfecting several long-contemplated inventions. The manufactory, which had for a time been unusually slack, was again in full work. Several engines were in hand for the London brewers. Wedgwood had ordered an engine to grind flints;[260] and orders were coming in for rotative engines for various purposes, such as driving saw-mills in America and sugar-mills in the West Indies. Work was, indeed, so plentiful that Watt was opposed to further orders for rotatives being taken, as the drawings for them occupied so much time, and they brought in but small profit. “I see plainly,” said he, “that every rotation engine will cost twice the trouble of one for raising water, and will in general pay only half the money. Therefore I beg you will not undertake any more rotatives until our hands are clear, which will not be before 1785. We have already more work in hand than we have people to execute it in the interval.”[261]
One reason why Watt was more than usually economical of his time was, that he was then in the throes of the inventions patented by him in the course of this year. Though racked by headaches which, he complained, completely “dumfounded” him and perplexed his mind, he could not restrain his irrepressible instinct to invent; and the result was the series of inventions embodied in his patent of 1784, including, among other things, the application of the steam-engine to the working of a tilt-hammer for forging iron and steel, to driving wheel-carriages for carrying persons and goods, and for other purposes. The specification also included the beautiful invention of the parallel motion, of which Watt himself said, “Though I am not over anxious after fame, yet I am more proud of the parallel motion than of any other mechanical invention I have ever made.” Watt was led to meditate this contrivance by the practical inconvenience which he experienced in communicating the direct vertical motion of the piston-rod by means of racks and sectors, to the angular motion of the working beam. He was gradually led to entertain the opinion that some means might be contrived for accomplishing this object by motions turning upon centres; and, working upon this idea, he gradually elaborated his invention. So soon as he caught sight of the possible means of overcoming the difficulty, he wrote to Boulton in Cornwall,—
“I have started a new hare. I have got a glimpse of a method of causing a piston-rod to move up and down perpendicularly by only fixing it to a piece of iron upon the beam, without chains or perpendicular guides or untowardly friction, arch heads, or other pieces of clumsiness; by which contrivance it answers fully to expectation. About 5 feet in the height of her house may be saved in 8-feet strokes, which I look upon as a capital saving, and it will answer for double engines as well as for single ones. I have only tried it in a slight model yet, so cannot build upon it, though I think it a very probable thing to succeed. It is one of the most ingenious, simple pieces of mechanism I have ever contrived, but I beg nothing may be said on it till I specify.”[262]
THE PARALLEL MOTION.
He immediately set to work to put his idea to the practical proof, and only eleven days later he wrote,—
“I have made a very large model of the new substitute for racks and sectors, which seems to bid fair to answer. The rod goes up and down quite in a perpendicular line without racks, chains, or guides. It is a perpendicular motion derived from a combination of motions about centres—very simple, has very little friction, has nothing standing higher than the back of the beam, and requires the centre of the beam to be only half the stroke of the engine higher than the top of the piston-rod when at lowest, and has no inclination to pull the piston-rod either one way or another, only straight up and down.... However, don’t pride yourself on it—it is not fairly tried yet, and may have unknown faults.”[263]
