Along in the month of November he wrote a vigorous protest against Cruikshank's explanation of the mode of formation of carbon monoxide. In this polemic he of course threw into prominence his precious phlogiston, the presence of which seemed unnecessary--but this was not so thought by the Doctor, who also favored the _Medical Repository_ with observations on the conversion of iron into steel, in which there is but a single reference to phlogiston, but unfortunately this single reference spoils the general argument and the correct and evident interpretation of the reaction. It reads as follows: Iron is convertible into steel by imbibing only _phlogiston_ from the charcoal with which it is cemented. There are abundant correct observations. Their interpretation sadly enough is very false, all because of the persistent introduction of phlogiston where it was not essential. Priestley advised Rush that because of an unhealthy season he had suffered very much from ague, and said,-- Tho' I was never robust, I hardly knew what sickness was before my seizure in Philadelphia, but the old building has since that had so many shocks, that I am apprehensive it will ere long give way. But I have abundant reason to be satisfied, and shall retire from life _conviva satur_. Devotion to work was on the part of Priestley, something marvelous. As his son and daughter-in-law were drawn to Philadelphia in February, 1803, they carried their father with them. He was rather indisposed to this, yet he disliked remaining alone at home notwithstanding the printing of the Church History required considerable personal attention. The marvelous part of it all was that while in Philadelphia, on this his fourth and last visit, while he fraternized with congenial souls and even presented himself at various social functions, he yet found leisure to print his little volume entitled "Socrates and Jesus Compared," which gave much pleasure to President Jefferson, so much indeed that he hoped Priestley would,-- take up the subject on a more extended scale, and show that Jesus was truly the most innocent, most benevolent, the most eloquent and sublime character that has ever been exhibited to man. Jefferson's genuine approval of his effort was balm to Priestley's soul. He, of course, wrote Lindsey and Belsham about it; yes, copied the letter of Jefferson and sent the same to them with the comment,-- He is generally considered as an unbeliever. If so, however, he cannot be far from us, and I hope in the way to be not only _almost_, but _altogether_ what we are. It was February 28, 1803, that the august members of the American Philosophical Society resolved: