“For the last four years of his life he lived under an administration, the principles and practice of which he perfectly approved, and with Mr Jefferson, the head of that administration, he frequently corresponded, and they had for each other a mutual regard and esteem. He enjoyed the esteem of the wisest and best men in the country, particularly at Philadelphia, where his religion and his politics did not prevent his being kindly and cheerfully received by great numbers of opposite opinions in both, who thus paid homage to his knowledge and virtue.” In 1800 he put together his last scientific work, and the one which he regarded as the crown of all his efforts, _viz._, his _Doctrine of Phlogiston Established_. It can never be said of Priestley that he was to one thing constant never: versatile as he was, and with an extraordinary capacity for adaptation and change in matters of philosophy and theological doctrine, he was ever constant to phlogiston. During the spring of 1801, whilst on a visit to Philadelphia, he had an attack of fever from which he never wholly recovered. It left him predisposed to the fever and ague at that time prevalent at Northumberland and he had a succession of attacks which weakened him greatly. Nevertheless, his spirits were uniformly good and his complacency and cheerfulness of manner never left him; and although he was incapable of taking much physical exercise and had to give up working in his garden, he spent a considerable amount of time in his laboratory, experimenting with all the enthusiasm and eagerness of his most active period with the newly-discovered pile of Volta, and sending his results to _Nicholson’s Journal_. In 1802 he was enabled to send his _Church History_ to press, owing to the action of his friends in England, who, unknown to him, had set a subscription on foot sufficient to cover the expense of publication. Although he was obviously failing in strength, owing to gastric troubles, he continued to work on either in his study or in his laboratory. He sent a couple of papers to the American Philosophical Society on scientific subjects, and he published an essay on _Jesus and Socrates Compared_. In the November of 1803 it was evident that his end was approaching. Still he struggled on, hoping by careful attention to his diet he might still see the spring. He told the physician who attended him that if he could but patch him up for six months longer he should be perfectly satisfied, as he should in that time be able to complete the printing of his works. So precarious did he consider his life that he took the precaution of transcribing one day in longhand what he had composed the day before in shorthand, that he might by that means leave the work complete as far as it went should he not live to finish the whole.