Priestley’s Career in England

After Priestley left the Daventry Dissenting Academy, his career took him to many parts of England, as he was “called” from one religious community to another as preacher and teacher. Not all his posts were successful: his first one in a rural community in Suffolk he called “a low, despised situation,” and his fierce Unitarian views were too much for his congregation, which, together with his income, dwindled. But from time to time he was able to slip into nearby Cambridge, and he started to teach science to his parishioners, building up a collection of scientific apparatus. He transferred to Nantwich, home of the salt industry, and then to Warrington, where he began serious teaching at the newly established academy. Priestley’s remarkably polymathic abilities are clearly shown by his syllabus for 1762, which announces that for that year he will teach Latin and Greek language and antiquities, French, English grammar, oratory, history, logic, and anatomy. And it was in the same year that he published A Course of Lectures on the Theory of Language and Universal Grammar. A year later he started teaching chemistry, and it was not long before he started his own researches.

But his major concern was static electricity; we must remember that the electric cell was not invented by Alessandro Volta until the end of Priestley’s life. Priestley repeated earlier experiments and incorporated his own, publishing the substantial volume The History and Present State of Electricity, with Original Experiments in 1767. He had already been awarded an honorary doctorate by Edinburgh University for his educational activity, and he was made a fellow of the Royal Society in 1766. So at the young age of 33, his potential, if not actual, achievements had been recognized.

Priestley’s moves from one appointment to another read almost as a travel itinerary. After six years at Warrington, he moved to Leeds, a Yorkshire center of the wool industry that would burgeon into one of the great industrial cities of northern England. Here Priestley conceived the development of a major work, starting with the electricity volume, which he intended to expand into an encyclopedia of all known physical science. This he was to call The History of All Branches of Experimental Philosophy. His next volume was on optics: History and Present State of Discoveries relating to Vision, Light and Colours, and this was followed by what was his greatest scientific achievement in print, six volumes of his chemical studies, called Experiments and Observations on Different Kinds of Airs, published between 1774 and 1786. These volumes describe, among other things, his experiments on gases, including his discovery of oxygen, which he stubbornly considered to be dephlogisticated air.

It is difficult for us to enter the mind-set of the experimenter of this time. Gases were by no means understood as distinct chemical substances, with distinct properties, let alone as being made of distinct chemical components. Though it had been appreciated that gases with different colors and smells existed, this variety was ascribed to there being a single gas, called air, in different states of purity. It was not until the Edinburgh medical student Joseph Black chemically characterized carbon dioxide, which he called fixed air, in 1754, that the realization occurred that different gases were in fact different chemical substances. Priestley occupied himself furiously with developing an understanding of gases, working on a greater range of them than anybody else.