In 1766 we find him engaged in a correspondence with the distinguished Benjamin Franklin as to steam power. Eight years before, Franklin had visited Boulton at Birmingham and made his acquaintance. They were mutually pleased with each other, and continued to correspond during Franklin’s stay in England, exchanging their views on magnetism, electricity, and other subjects.[110] When Boulton began to study the fire-engine with a view to its improvement, Franklin was one of the first whom he consulted. Writing him on the 22nd February, 1766, he said,--
“My engagements since Christmas have not permitted me to make any further progress with my fire-engine; but, as the thirsty season is approaching apace, necessity will oblige me to set about it in good earnest. Query,--Which of the steam-valves do you like best? Is it better to introduce the jet of cold water at the bottom of the receiver, or at the top? Each has its advantages and disadvantages. My thoughts about the secondary or mechanical contrivances of the engine are too numerous to trouble you with in this letter, and yet I have not been lucky enough to hit upon any that are objectionless. I therefore beg, if any thought occurs to your fertile genius which you think may be useful, or preserve me from error in the execution of this engine, you’ll be so kind as to communicate it to me, and you’ll very greatly oblige me.”
[110] On the 22nd May, 1765, Franklin writes Boulton,--“Mr. Baskerville informs me that you have lately had a considerable addition to your fortune, on which I sincerely congratulate you. I beg leave to introduce my friend Doctor Small to your acquaintance, and to recommend him to your civilities. I would not take this freedom, if I were not sure it would be agreeable to you; and that you will thank me for adding to the number of those who from their knowledge of you must respect you, one who is both an ingenious philosopher and a most worthy honest man. If anything new in magnetism or electricity, or any other branch of natural knowledge, has occurred to your fruitful genius since I last had the pleasure of seeing you, you will by communicating it greatly oblige me.”
From a subsequent letter it appears that Boulton, like Watt--who was about the same time occupied with his invention at Glasgow--had a model constructed for experimental purposes, and that this model was now with Franklin in London; for we find Boulton requesting the latter to “order a porter to nail up the model in the box again and take it to the Birmingham carrier at the Bell Inn, Smithfield.” After a silence of about a month Franklin replied,--