A Letter from the Reverend William Derham. D. D. Canon of Windsor, and F. R. S. to Sir Hans Sloane, Bart. Proes. Coll. Med. et R. S. concerning the Frost in January, 1730/1

camentorum, an cerevisiae illius, an naturae beneficio disrupti & expulsi sint. Ex segmentis frustulorum valde convexis, quae hic mitto, & quae adhuc adservo, judicare licet, vix ullum illorum calculorum nucem moschatam superasse, plures vero minores fuisse. Interea tamen solutionem calculorum in vesica haud prorsus impossibilem esse, mihi evincere videntur, licet res forte quam rarissime contingat. Vale mihique fave. Dab. Helmstadii in Academia Julia ipsis Calendis Octobris, M DCC XXX. IV. A Letter from the Reverend William Derham, D.D. Canon of Windsor, and F.R.S. to Sir Hans Sloane, Bart. Praef. Coll. Med. & R.S. concerning the Frost in January, 1732. The late Frost having been almost as intense as any that hath been for many Years, I send you my Account of it; which if you think worth the Cognizance of the Royal Society, be pleased to impart it to them. In the Philosophical Transactions for November and December, 1709, Numb. 324, I have given an Account of some of the most remarkable Frosts that I could find any Relation of; and particularly of that great and, I had almost said, universal one in 1708, which the Society had very good Histories of from divers Parts, and which, in that Transaction, I have given an Account of from the Original Papers, which the Society was pleased to do me the Honour to entrust me with. In that Transaction I have made it very probable, that the greatest Descent of the Spirits in the Thermometer, was on December 30, 1708, when my Glass was within one Tenth of an Inch as low as it is with artificial Freezing with Snow or Ice and Salt: And in the late Frost it was almost, if not altogether, as low. The Freezing-Point of my Thermometer is 10 Inches (which I call 100 Degrees) above the Globe of Spirits; and the most intense Freezing (according to the Methods I have mentioned in that Transaction) is just at, or very little within the Ball. And on January 30, about Sun-rising, the Thermometer was but an Inch, or 10 Degrees above the Point of extreme Freezing; and on February 3, at only half an Inch, or 5 Degrees. And considering that the Thermometer I observed with in 1708, was less accurate, and differently graduated from that which I now have, I am apt to think, that the Frost on February 3 last, was altogether as intense as that on December 30, 1708. For although a Frigorifick Mixture sunk the Spirits but one Tenth lower in the old Thermometer, and about 5 or 6 Tenths in that I now observe with, yet I take the Difference to be little, or none at all, by reason of the Tenderness of the new above the old Glass. And this Degree of Cold I take to be as excessive as in any of the Years mentioned in the said Transaction; yea, any of the Years, when the Thames at London was frozen over: I am sure colder than in the Year 1716, when when that River was frozen over for several Miles, and Booths and Streets were made on the Ice, an Ox roasted thereon, &c. For the lowest Point of Freezing in 1716, was on January 7, when the Spirits fell to 35 Degrees only of the Glass I now make use: But the true Cause of the freezing of the Thames that Year was not barely the Excess of the Cold, but the long Continuance of it: Which was also the principal Cause of those remarkable Congelations of that River in 1683 and 1708, when I saw Coaches driven over the Ice, large Fires made on it, &c. I am, with great Respect, Honoured SIR, Upminster, Feb. 13th, 1739. Yours, WILLIAM DERHAM. V. A Letter to Cromwell Mortimer, M.D. Secr. R.S. containing several Experiments concerning Electricity; by Mr. Stephen Gray. SIR, In the Year 1729 I communicated to Dr. Desaguliers, and some other Gentlemen, a Discovery I had then lately made, shewing that the Electric Virtue of a Glass Tube may be conveyed to any other Bodies, so as to give them the same Property of attracting