“What you propose,” Watt wrote, “is exceeding probable, and akin to what I have long contemplated--the use of mixed air and steam, which have a wonderful expansion and contraction. Nevertheless, I fear that there is in all such cases a proportional assumption of latent heat; but be it tried though it be beginning a new series of vexations and expense.... I suspect that a forcible compression would hinder the gas from separating from the water, and on the contrary any tolerable degree of vacuum would hinder the water from attracting it; but perhaps part of both may be used.... My greatest hope is in the expansive engine with double or single cylinder, which I consider as proved by many facts, and shall send you my ideas of the execution of it very soon. At the same time I am clear to take the air patent, which, as I have worded the petition, may include some other improvements on the steam-engine.... I hope my last letters have relieved you, as the knowledge of the Horners’ being a steam-engine working on our principle relieved me. I have some trust in the judges, though I have little in the law; and I think impartial people will regard us as injured persons, and not suffer the thief of our horse to escape because he has painted him of another colour.”[221] [221] Watt to Boulton, 28th July, 1781. A few days later Boulton wrote Watt that Dr. Priestley had proceeded with the experiments, and that he had come to the conclusion that “there is nothing to be feared from any of the tribe of gases, which cannot be produced nearly so cheap as steam; and as to steam _you_ know its limits better than any man.” Watt’s fears for his patent were about this time excited anew by the great Arkwright trial, in which Arkwright was nonsuited, and compelled to forego the rights derived from his improvements and combinations of spinning-machinery. The principal ground on which the patent was set aside was that the specification was unintelligible. On this, Watt observed,-- “Though I do not love Arkwright, I don’t like the precedent of setting aside patents through default of specification. I fear for our own. The specification is not perfect according to the rules lately laid down by the judges. Nevertheless, it cannot be said that we have hid our candle under a bushel. We have taught all men to erect our engines, and are likely to suffer for our pains.... I begin to have little faith in patents; for, according to the enterprising genius of the present age, no man can have a profitable patent but it will be pecked at, and no man can write a specification of a fire-engine that cannot be evaded, if the words and not the true intent and meaning be attended to. As kissing goes by favour, and as, in dubious cases, men are actuated by their prejudices, so, where a blue is very like a green they may decide either way.”[222]