Boulton returned to Soho greatly improved in health, and was shortly immersed as before in the business of the factory. He found considerable arrears of correspondence requiring to be brought up. Several of the letters waiting for him were from schemers of new inventions connected with the steam-engine. Whenever an inventor thought he had discovered anything new, he at once rushed to Boulton with it. He was looked upon as the lord and leader of steam power. His reputation for enterprise and business aptitude, and the energetic manner in which he had pushed Watt’s invention, were now so widely known, that every new schemer saw a fortune within his reach could he but enlist Boulton on his side. Hence much of his time was occupied in replying to letters from schemers,--from inventors of perpetual motion, of flying-machines, of locomotion by steam, and of various kinds of rotary motion. In one of his letters we find him complaining of so much of his time being “taken up in answering great numbers of letters he had lately been plagued with from eccentric persons of no business;” for it was his practice never to leave a letter unanswered, no matter how insignificant or unreasonable his correspondent might be.[258] [258] With an almost excess of politeness, Boulton wrote long letters to unknown correspondents to set them right about mechanical errors into which they seemed to him to have fallen. Thus a Mr. Knipe of Chelsea, supposing he had discovered a perpetual motion machine, wrote inviting Boulton to join him as a partner. Though the man was without means and evidently foolish, Boulton wrote him several long letters in the kindest spirit, pointing out that his scheme was contrary to reason and science. “It is impossible,” said he, “for inanimate mechanism to _produce_ the least degree of power or to augment the sum total of the _primum mobile_. Mechanism may communicate or concentrate or economise power, but cannot create or augment it.” Knipe replied at great length, vindicating his invention. His enthusiasm pleased Boulton, who, in the generosity of his nature, sent him a draft for ten guineas on his London bankers to enable the poor inventor to secure his invention if there was really anything in it. But nothing more was heard of Knipe’s Perpetual Motion Machine.