They represent the results of inquiries performed under unusual surroundings. It is very probable that Priestley's English correspondents desired him to concentrate his efforts upon experimental science. They were indeed pleased to be informed of his Church History, and his vital interest in religion, but they cherished the hope that science would in largest measure displace these literary endeavors. Priestley himself never admitted this, but must have penetrated their designs, and, recognizing the point of their urging, worked at much disadvantage to get the results presented in these two pioneer studies. Present day students would grow impatient in their perusal, because of the persistent emphasis placed on phlogiston, dephlogisticated air, phlogisticated air, and so forth. In the very first paper, the opening lines show this:
It is an essential part of the antiphlogistic theory, that in all the cases of what I have called phlogistication of air, there is simply an absorption of the dephlogisticated air, or, as the advocates of that theory term it, the oxygen contained in it, leaving the phlogisticated part, which they call azote, as it originally existed in the atmosphere. Also, according to this system, azote is a simple
substance, at least not hitherto analyzed into any other.
No matter how deeply one venerates Priestley, or how great honor is ascribed to him, the question continues why the simpler French view was not adopted by this honest student. Further, as an ardent admirer one asks why should Priestley pen the next sentence:
They, therefore, suppose that there is a determinate proportion between the quantities of oxygen, and azote in every portion of atmospherical air, and that all that has hitherto been done has been to separate them from one another. This proportion they state to be 27 parts of oxygen and 73 parts of azote, in 100 of atmospherical air.
Priestley knew that there was a "determinate proportion." He was not, however, influenced by quantitative data.
Sir Oliver Lodge said[4]—
Priestley's experiments were admirable, but his perception of their theoretical relations
was entirely inadequate and, as we now think, quite erroneous.... In theory he had no instinct for guessing right ... he may almost be said to have had a predilection for the wrong end.
At present the French thought is so evident that it seems incomprehensible that Priestley failed to grasp it, for he continues—