a scientific student, and the peaceful practice of the art of medicine, for the stormy sea of political strife in a peculiarly troublous time. The following letter to Robert Boyle may, therefore, be deemed no unfitting termination to the narrative of this period of his career:
'A letter from Mr. William Petty to the Honourable Robert Boyle, Esq., dated from Dublin, April 15, 1653.
'Sir,—Being not able to write you any such complements as may delight you, nor to enforme you of any such more real matter as might profit you, I desire that those my deficiencies, together with my usual rudeness, may be taken for the cause of this long silence. Now indeed I am forced to communicate with you, even to keep up the face of the visible church of philosophers; for by Mr. Worsely his going for England and Major Morgan's absence in the North, there is no such thing now left at the headqters. If there be any other reason of these lines besides this, and to beg my continuance in the number of your affectionate servants, it is to dissuade you from some things, which my lord of Corke, my lord of Broghill, and some other of your friends think prejudicial unto you: one whereof is your continual reading. Here, like a Quacksalver, I might tell you how it weakens the brain, how that weakness causeth defluxions and how those defluxions hurt the lungs and the like. But I had rather tell you that although you read 12 hours per diem or more, that you shall really profit by no more of what you read, than by what you remember; nor by what you remember, but by so much as you understand and digest; nor by that, but by so much as is new unto you, and pertinently set down. But in 12 hours how little (according to these rules) can you (who know so much already) advantage yourself by this laborious way? How little of true history doe our books contain? How shy is every man to publish anything either rare or useful? How few opinions doe they deliver rationally deduced but from their own principles? and lastly how few doe begin their tedious systems from principles possible, intelligible and easy to be admitted?
