The “Invisible College,” the embryo of the Royal Society of London, was then already in existence. Since some time in 1645, a little club composed of a few “worthy persons inquisitive into natural philosophy” had been holding its weekly meetings; sometimes in the lodging of the physician, Dr. Jonathan Goddard, in Wood Street, Cheapside; sometimes at a “convenient place” in Cheapside itself,—in fact, the Bull’s Head Tavern; and sometimes in Gresham College, near by. Its originator was Theodore Haak, who, like Hartlib, was a naturalised German; and among its first members were Dr. John Wallis, clerk to the Westminster Assembly; Dr. Wilkins, afterwards Warden of Wadham College, Oxford, and brother-in-law of Oliver Cromwell; Foster, the professor of astronomy at Gresham College; the young William Petty; Dr. Goddard himself; and one or two other “doctors in physic” more or less well known in London. They had their telescopes and microscopes and their attendant apothecaries, etc.; and, “precluding theology and state-affairs,” they wandered at will among the sciences,—the physics and chemics, and mechanics and magnetics,—“as then cultivated at home and abroad.” Hartlib was from the very first connected with this club: “The Invisible College of his imagination seems to have been that enlarged future association of all earnest spirits for the prosecution of real and fruitful knowledge of which this club might be the symbol and promise.”[144] His early letters to Robert Boyle at Stalbridge are full of the subjects under discussion. And there is no doubt that it was to a great extent the fascination of these weekly meetings in Wood Street, and the company he met there, that drew Robert Boyle so often to London and kept him in London as long as he could manage to stay there. “I have been every day these two months,” he wrote to his friend Francis Tallents, in February 1647,[145] “upon visiting my own ruined cottage in the country; but it is such a labyrinth, this London, that all my diligence could never yet find a way out on’t ... the best on’t is, that the corner-stones of the _invisible_, or as they term themselves, the _philosophical college_, do now and then honour me with their company ... men of so capacious and searching spirits, that school-philosophy is but the lowest region of their knowledge; and yet, though ambitious to lead the way to any generous design, of so humble and tractable a genius, as they disdain not to be directed to the meanest, so he can but plead reason for his opinion; persons that endeavour to put narrow-mindedness out of countenance by the practice of so extensive a charity that it reaches unto everything called man, and nothing less than a universal goodwill can content it. And indeed they are so apprehensive of the want of good employment, that they take the whole body of mankind for their care.”