I have many excellent good notes from him as to mechaniques, etc., and I never was with him but I learn't, and alwayes tooke notes; but now indeed the Royall Societie haz out-donne most of his things, as having a better apparatus, and more spare money. I have a curious designe of his to drawe a landskip or perspective (1656), but Sir Christopher Wren hath fallen on the same principle, and the engine is better work't. He was smyth and joyner enough to serve his turne, but he did not pretend to curiosity in each. He gave me a quadrant in copper, and made me another in silver, of his owne projection, which serves for all latitudes. He shewed me, 1649, the best way of making an arch was a parabola with a chaine; so he tooke of his girdle from his cassock, and applyed it to the wall, thus:
He invented and made with his owne handes a paire of beame[725] compasses, which will divide an inch into a hundred or a thousand parts. At one end of the beame[725] is a roundle, which is divided into 100 equall parts, with a sagitta to turne about it with a handle: this handle turnes a skrew of a very fine thread, and on the back of the saile or beame is a graduation. With these compasses he made the quadrants aforesayd. He gave me a paire of these compasses, which I shewed to the[726] Royall Societie at their first institution, which they well liked, and I presented them as a rarity to my honoured friend, Edmund Wyld, esqre. There are but[727] two of them in the world.
☞ Memorandum that at the Epiphanie, 1649, when I was at his house, he then told me his notion of curing diseases, etc. by transfusion of bloud[LXI.] out of one man into another, and that the hint came into his head reflecting on Ovid's story of Medea and Jason, and that this was a matter of ten yeares before that time. About a yeare after, he and I went to trye the experiment, but 'twas on a hen, and the creature to little and our tooles not good: I then sent him a surgeon's lancet. Anno ... I recieved a letter from him concerning this subject, which many yeares since I shewed, and was read and entred in the bookes of the Royall Societie, for Dr. Lower would have arrogated the invention to himselfe, and now one [R.[728] Griffith,] Dr. of Physique, of Richmond, is publishing a booke of the transfusion of bloud, and desires to insert Mr. Potter's letter: which I here annex in perpetuam rei memoriam.
[LXI.] Memorandum:—Mr. Meredith Lloyd tells me that Libavius speakes of the transfusion of bloud, which I dare sweare Mr. F. Potter never sawe in his life.
[729]'Worthy Sir,
'I am sorrie that I can as yet give you no better account of that experiment of which you desire to heare. I am as yet frustrated in ipso limine (but it is by my owne unexpertnes, who never attempted any such thing upon any creature before); for I cannot, although I have tried divers times, strike the veine so as to make him bleed in any considerable quantity.
'I have prepared a little cleare transparent vessel (like unto a bladder), made of the[730] craw of a pullet; and I have fastened an ivory pipe to one of the neckes of it, and I have put it into a veine which is most conspicuous about the lowest joint of the hinder legges; and yet I cannot procure above 2 or 3 drops of blood to come into the pipe or the bladder.
