After this apologia, Priestley gives the reins to his imagination, or rather he allows phlogiston to drive the halting, ambling thing for him, with the result that he utterly loses his way and is eventually landed into an impassable quagmire. It is not too much to say that not one of the “Queries, Speculations and Hints” with which the volume closes has stood the test of time.
The second volume, which made its appearance towards the end of 1775, is dedicated to Sir John Pringle, at that time President of the Royal Society. It opens, as usual, with a somewhat prolix but characteristic preface. But to his biographer Priestley’s prefaces are not the least interesting or valuable of his literary productions.
“In a preface,” he says, “authors have always claimed a right of saying whatever they pleased concerning themselves, and not to lose this right it must now and then be exercised.”
In this respect Priestley has championed the prerogatives of authors for all time. This particular preface begins with an expression of self-laudation for the little delay the writer made in putting the first volume to the press.
“In consequence of this considerable discoveries have been made by people of distant nations; and this branch of science, of which nothing, in a manner, was known till very lately, indeed now bids fair to be farther advanced than any other in the whole compass of natural philosophy.... And it will not now be thought very assuming to say that by working in a tub of water or a basin of quicksilver we may perhaps discover principles of more extensive influence than even that of gravity itself, the discovery of which, in its full extent, contributed so much to immortalise the name of Newton.
“Having been the means of bringing so many champions into the field, I shall, with peculiar pleasure, attend to all their achievements, in order to prepare myself, as I promised in the preface to my last volume, for writing the history of the campaign.”
After a delightfully naïve compliment to his own ability as an accumulator of facts, and to his merits as an “instrument in the hands of Divine Providence ... concerning which I threw out some further hints in my former preface, which the excellent French translator was not permitted to insert in his version,” he advances this testimony to his impartiality as an historian:—
“I even think that I may flatter myself so much, if it be any flattery, as to say that there is not, in the whole compass of philosophical writing, a history of experiments so truly ingenuous as mine, and especially the section on the discovery of dephlogisticated air, which I will venture to exhibit as a model of the kind. I am not conscious to myself of having concealed the least hint that was suggested to me by any person whatever, any kind of assistance that has been given me, or any views or hypotheses by which the experiments were directed, whether they were verified by the result or not.”
There is much else in the preface that might be quoted as illustrative of the character and mental attributes of its author. Priestley, the natural philosopher, never forgot that he was a minister of religion, and that to him theology was the greatest and most important of all the sciences, and he cannot forbear even, in what he intended to be a scientific disquisition on purely natural phenomena, from inculcating his belief in the divine origin of Christianity and his opinion concerning the doctrine of purgatory and the worship of the dead.
The first chapter is concerned with the discovery of what its author called Vitriolic Acid Air, but which we now know as sulphur dioxide.