On the 23rd of July he returned to the subject:—
“The Horners,” said he, “continue bragging of what they are to do, and I hear the country in general takes part with them, as even the aversion they have to the Horners does not equal the pleasure they would feel at our undoing.... The Horners say they can make a common engine equal to ours, but that their new engine is one-third better. We must now attend to making use of all the elastic power of the steam, which, unless I am much deceived, will save one-half over our best engines, and at any rate it may easily be applied to work the condenser, which will save about one-eighth. I will not conceal from you that I am rendered very unhappy by one thing and another, but fight with it all I can.”
In the mean time Boulton continued to urge Watt to complete the specification and drawings of his rotative engine, informing him of the success of the model which he had now completed at Soho:—
“Though you studied a thousand years,” said he, “I do not think you could make one ten per cent. better than a small model with two cones which Joseph has executed after my drawings. It has little friction, goes sweeter than anything of the kind you have yet touched, and has not the least shake. It is so perfect that I don’t consider it worth while even to think of any other for horizontal motions. I am therefore positively decided in my mind as to the necessity of taking out a patent and including in it all the principles and constructions you please; for if it be not secured soon we may lose it.”[217]
In the same letter, Boulton communicated to Watt the rumours that had reached him from Scotland of more inventions of engines that were to beat Watt’s out of the field. “The cry is still, they come!” said he. “Hatley from Scotland is going with Lord Dunmore to Virginny; says that he and somebody else in Scotland have invented an engine that is three times better than yours.” Boulton recommended that a search should be made at the Patent-Office, to ascertain what was going on in new engine patents. Watt entirely approved of this, and urged that the search should be made at once. “I do not think we are safe a day to an end,” he wrote, “in this enterprising age. One’s thoughts seem to be stolen before one speaks them. It looks as if Nature had taken an aversion to monopolies, and put the same thing into several people’s heads at once to prevent them; and I begin to fear that she has given over inspiring me, as it is with the utmost difficulty that I can hatch anything new.”
Notwithstanding this confession on the part of Watt, his inventive faculties were really never at any period of his life more vigorous than now; for he was rapidly maturing his rotative engine, with its various ingenious methods for securing circular motion; and working out the details of the double-cylinder expansion engine, with its many admirable contrivances hereafter to be described. Boulton continued to receive applications at Soho, from various quarters, for engines capable of working flour-mills and other machinery, and Watt himself was urged by like inquiries from manufacturers in Cornwall. “Mr. Edwards,” he wrote Boulton, “waits impatiently the success of our rotative machine. He wants a power able to lift a hammer of 700 lbs., 2 feet high, 120 times per minute.... In relation to the circular engine, an experiment should be made on a large scale, and to work a hammer. I want your ideas on that head.”[218] A fortnight later, Watt had matured his own ideas, and made the necessary declaration of his invention before a magistrate, preliminary to making the usual application for a patent.[219]
Watt was exceedingly busy about this time in superintending the erection of new engines. No fewer than twelve were in progress in different parts of the county. As he travelled about from one mine to another on horseback, and spent a good deal of his time in the open air, his mind was diverted from preying upon itself according to his ordinary habit, and his health and spirits improved accordingly. Boulton was equally busy at Soho, where he was erecting a powerful engine for blowing the furnaces at Walker’s ironworks at Rotherham, and another for Wilkinson’s forges at Bradley, in which he proposed to employ a double cylinder, with a double crank[220] and a pair of fly-wheels. At intervals he went into Yorkshire, Lancashire, and Shropshire, to look after various other engines in progress; writing Watt cheerful letters as to the improving prospects of the firm. He found the steam-engine everywhere gaining in public estimation. “The more it is known,” he wrote, “the more it will be in demand. As to the scheme of the Hornblowers, they shall sooner press me down into the earth than they shall press down a piston with steam.” And again, “Give yourself no uneasiness about the Horners’ engine. Our title to the invention is as clear as can be; and it is as well secured as an Act of Parliament can make it—
“Doubt that the sun is fire,
Doubt all the powers of sight,
Doubt truth to be a lyer,