CHAPTER X.
Boulton and the Steam Engine—Correspondence with Watt.
Want of water-power was one of the great defects of Soho as a manufacturing establishment, and for a long time Boulton struggled with the difficulty. The severe summer droughts obliged him to connect a horse-mill with the water-wheel. From six to ten horses were employed as an auxiliary power, at an expense of from five to eight guineas a week. But this expedient, though costly, was found very inconvenient. Boulton next thought of erecting a pumping-engine after Savery or Newcomen’s construction, for the purpose of raising the water from the mill-stream and returning it back into the reservoir—thereby maintaining a head of water sufficient to supply the water-wheel and keep the mill in regular work. “The enormous expense of the horse-power,” he wrote to a friend, “put me upon thinking of turning the mill by fire, and I made many fruitless experiments on the subject.”
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.”
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,—
“You will, I trust, excuse my so long omitting to answer your kind letter, when you consider the excessive hurry and anxiety I have been engaged in with our American affairs.... I know not which of the valves to give the preference to, nor whether it is best to introduce your jet of cold water above or below. Experiments will best decide in such cases. I would only repeat to you the hint I gave, of fixing your grate in such a manner as to burn all your smoke. I think a great deal of fuel will then be saved, for two reasons. One, that smoke is fuel, and is wasted when it escapes uninflamed. The other, that it forms a sooty crust on the bottom of the boiler, which crust not being a good conductor of heat, and preventing flame and hot air coming into immediate contact with the vessel, lessens their effect in giving heat to the water. All that is necessary is, to make the smoke of fresh coals pass descending through those that are already thoroughly ignited. I sent the model last week, with your papers in it, which I hope got safe to hand.”[111]
The model duly arrived at Soho, and we find Boulton shortly after occupied in making experiments with it, the results of which are duly entered in his note-books. Dr. Erasmus Darwin, with whom he was on very intimate terms, wrote him from Lichfield, inquiring what Franklin thought of the model and what suggestions he had made for its improvement. “Your model of a steam-engine, I am told,” said he, “has gained so much approbation in London, that I cannot but congratulate you on the mechanical fame you have acquired by it, which, assure yourself, is as great a pleasure to me as it could possibly be to yourself.”[112] Another letter of Darwin to Boulton is preserved, without date, but apparently written earlier than the preceding, in which the Doctor lays before the mechanical philosopher the scheme of “a fiery chariot” which he had conceived,—in other words, of a locomotive steam-carriage. He proposed to apply an engine with a pair of cylinders working alternately, to drive the proposed vehicle;[113] and he sent Boulton some rough diagrams illustrative of his views, which he begged might be kept a profound secret, as it was his intention, if Boulton approved of his plan and would join him as a partner, to endeavour to build a model engine, and, if it answered, to take out a joint patent for it. But Dr. Darwin’s scheme was too crude to be capable of being embodied in a working model; and nothing more was heard of his fiery chariot.
Another of Boulton’s numerous correspondents about the same time was Dr. Roebuck, of Kinneil, then occupied with his enterprise at Carron, and about to engage in working the Boroughstoness coal mines, of the results of which he was extremely sanguine. He also wished Boulton to join him as a partner, offering a tenth share in the concern, and to take back the share if the result did not answer expectations. But Boulton’s hands were already full of business nearer home, and he declined the venture. Roebuck then informed him of the invention made by his ingenious friend Watt, and of the progress of the model engine. This was a subject calculated to excite the interest of Boulton, himself occupied in studying the same subject, and he expressed a desire to see Watt, if he could make it convenient to visit him at Soho.
It so happened that Watt had occasion to be in London in the summer of 1767, on the business connected with the Forth and Clyde Canal Bill, and he determined to take Soho on his way home. When Watt paid his promised visit, Boulton was absent; but he was shown over the works by his friend Dr. Small, who had settled in Birmingham as a physician, and already secured a high place in Boulton’s esteem. Watt was much struck with the admirable arrangements of the Soho manufactory, and recognised at a glance the admirable power of organisation which they displayed. Still plodding wearily with his model, and contending with the “villanous bad workmanship” of his Glasgow artisans, he could not but envy the precision of the Soho tools and the dexterity of the Soho workmen. Some conversation on the subject must have occurred between him and Small, to whom he explained the nature of his invention; for we find the latter shortly after writing Watt, urging him to come to Birmingham and join partnership with Boulton and himself in the manufacture of steam-engines.[114] Although nothing came of this proposal at the time, it had probably some effect, when communicated to Dr. Roebuck, in inducing him to close with Watt as a partner, and thus anticipate his Birmingham correspondents, of whose sagacity he had the highest opinion.