At the time when he settled at Birmingham, Priestley was actively engaged in prosecuting inquiries into the constitution of bodies. He had been occupied for several years before in making investigations as to the gases. The discovery of carbonic acid gas by Dr. Black of Edinburgh, had attracted his attention; and, living conveniently near to a brewery at Leeds, where he then was, he proceeded to make experiments on the fixed air or carbonic acid gas evolved during fermentation. From these he went on to other experiments, making use of the rudest apparatus,—phials, tobacco-pipes, kitchen utensils, a few glass tubes, and an old gun-barrel. The pursuit was a source of constant pleasure to him. He had entered upon an almost unexplored field of science. Then was the childhood of chemistry, and he gazed with large-eyed wonder at the marvels which his investigations brought to light. He had no teacher to guide him—nothing but experiment; and he experimented constantly, carefully noting the results. Observation of facts was his great object; the interpretation of the facts he left to others. Such was Priestley, and such were his pursuits, when he settled at Birmingham in 1780.
There can be little doubt that his enthusiasm as an experimenter in chemistry exercised a powerful influence on the minds of both Boulton and Watt, who, though both full of work, anxiety, and financial troubles, were nevertheless found taking an active interest from this time forward in the progress of chemical science. Chemistry became the chief subject of discussion at the meetings of the Lunar Society, and chemical experiments the principal recreation of their leisure hours.
“I dined yesterday at the Lunar Society (Keir’s house),” wrote Boulton to Watt; “there was Blair, Priestley, Withering, Galton, and an American ‘rebel,’ Mr. Collins. Nothing new except that some of my white Spathos Iron ore was found to contain more air than any ore Priestley had ever tried, and, what is singular, it contains no common air, but is part fixable and part inflammable.”[296]
To Henderson, in Cornwall, Boulton wrote, two months later,—
“Chemistry has for some time been my hobby-horse, but I am prevented from riding it by cursed business, except now and then of a Sunday. However, I have made great progress since I saw you, and am almost an adept in metallurgical moist chemistry. I have got all that part of Bergmann’s last volume translated, and have learnt from it many new facts. I have annihilated Wm. Murdock’s bedchamber, having taken away the floor, and made the chicken kitchen into one high room covered over with shelves, and these I have filled with chemical apparatus. I have likewise set up a Priestleyan water-tub, and likewise a mercurial tub for experiments on gases, vapours, &c., and next year I shall annex to these a laboratory with furnaces of all sorts, and all other utensils for dry chemistry.”[297]
The “Priestleyan water-tub” and “mercurial tub,” here alluded to, were invented by Priestley in the course of his investigations, for the purpose of collecting and handling gases; and the pneumatic trough, with glass retorts and receivers, shortly became part of the furniture of every chemical laboratory.
Josiah Wedgwood was another member of the Lunar Society who was infected by Dr. Priestley’s enthusiasm for chemistry; and, knowing that the Doctor’s income from his congregation was small, he and Boulton took private counsel together as to the best means of providing him with funds so as to place him in a position of comparative ease, and enable him freely to pursue his investigations. The correspondence which took place on the subject is creditable to all parties concerned; and the more so to Boulton, as he was embarrassed at the time by financial difficulties of the most distressing kind, as has been already explained in a preceding chapter. Wedgwood had undertaken to sound Dr. Priestley, and he thus communicated the result to Boulton:—
“The Doctor says he never did intend or think of making any pecuniary advantage from any of his experiments, but gave them to the public with their results, just as they happened, and so he should continue to do, without ever attempting to make any private emolument from them to himself.
“I mentioned this business to our good friend, Dr. Darwin, who agrees with us in sentiment, that it would be a pity that Dr. Priestley should have any cares or cramps to interrupt him in the fine vein of experiments he is in the midst of, and is willing to devote his time to the pursuit of, for the public good. The Doctor will subscribe, and has thought of some friends who, he is persuaded, will gladly do the same....
“You will see by the enclosed list that one cannot decently exceed ten guineas unless it be under the cover of a friend’s name, which method I shall take if I think it necessary to write more than ten; but that is the subscription I shall begin with, and for three years certain.