But he was in Ireland again a month or two before Cromwell’s Protectorate was proclaimed in London, and living in Dublin through the winter of 1653-4. William Petty, his fellow-Invisible, was also there, and Benjamin Worsley, the old Army surgeon, a great friend of Hartlib and of the Boyle family. Petty had been appointed by Ireton physician-general to the Army, and was doing wonderful things in organisation, amongst other things saving the Government several hundreds a year in their drug department alone. Worsley, a delightful man in his way, full of the most astonishing scientific projects for the benefit of seventeenth-century science, had been appointed surveyor-general, to take in hand the land-survey necessary in the process of transplantation. In Petty’s opinion Worsley was a bit of a quack, whose “mountain-bellied conceptions” ended usually in “abortive mice”; and when Worsley began his survey Petty thought it could be better and quicker done, and said so. The Government backed Petty, in whom they had got hold of a man of extraordinary genius and energy; and while Worsley was kept on as surveyor-general, Petty was allowed to contract to do the work of land-survey in thirteen months, importing skilled labour and London-made instruments.[184] And meantime, Robert Boyle, under Petty’s guidance, was working quietly in an anatomical laboratory in Dublin. Petty, in his outspoken way, had written to Boyle while Boyle was on his flying visit to London in 1653. Petty and Robert Boyle’s own relations in Dublin were at this time a little anxious about Boyle’s health and spirits; and urged by the relatives, Petty had written in the character of physician and friend, offering Boyle some sound advice. He wrote to “dissuade” him from “some things which my lord of Cork, my lord of Broghill, and some others of your friends think prejudicial to you; one of which is your continual reading.” Too much reading, Petty thought, “weakens the brain,” which weakness “causeth defluxions” and these “hurt the lungs.” In Petty’s opinion Boyle, who knew so much already, could get but little advantage from the constant study of books. Warming with his subject, Petty adventures a little more advice. “The next disease you labour under is your apprehension of many diseases, and a continual fear that you are always inclining, or falling into, one or other.” He reminds Boyle how “this is incident to all that begin the study of diseases”; how “inward causes” may produce “different outward signs,” and those “little rules of prognostication, found in our books, need not always be so religiously believed.” And even if people do fall ill, do they not also sometimes get well again? “Why may not a man as easily recover of a disease, without much care, as fall into it?” And then, to wind up with: “The last indictment that I lay against you is, practising upon yourself with medicaments (though specifics) not sufficiently tried by those that administer or advise them.”