Read Priestley's volumes on Air and on Natural Philosophy. They are classics. All conversant with their contents agree that the experimental work was marvelous. Priestley's discovery of oxygen was epoch-making, but does not represent all that he did. Twice he just escaped the discovery of nitrogen. One wonders how this occurred. He had it in hand. The other numerous observations made by him antedate his American life and need not be mentioned
here. They alone would have given him a permanent and honorable rank in the history of chemistry. Students of the science should reserve judgment of Priestley until they have familiarized themselves with all his contributions, still accessible in early periodicals. When that has been done, the loss to English science, by Priestley's departure to another clime will be apparent.
His dearest friends would have held him with them. Not every man's hand was against him—on the contrary, numerous were those, even among the opponents of his political and theological utterances, who hoped that he would not desert them. They regretted that he had—
turned his attention too much from the luminous field of philosophic disquisition to the sterile regions of polemic divinity, and the still more thorny paths of polemic politics....
from which the hope was cherished that he would recede and devote all his might to philosophical pursuits.
A very considerable number ... of enlightened inhabitants, convinced of his
integrity as a man, sincerity as a preacher, and superlative merit as a philosopher, were his strenuous advocates and admirers.
But the die had been cast, and to America he sailed on April 8, 1794, in the good ship Sansom, Capt. Smith, with a hundred others—his fellow passengers. Whilst on the seas his great protagonist Lavoisier met his death on the scaffold.
Such was the treatment bestowed upon the best of their citizens by two nations which considered themselves as without exception the most civilized and enlightened in the world!
It is quite natural to query how the grand old scientist busied himself on this voyage of eight weeks and a day. The answer is found in his own words: