An Extract of a Letter from Mr Ralph Thoresby, F. R. S. to Dr Hans Sloane, S. R. S. concerning Some Swedish Coyns; And a Calculation for the Finding of Easter

VI. An Extract of a Letter from Mr Ralph Thoresby, F. R. S. to Dr Hans Sloane, S. R. S. concerning some Swedish Coyns; and a Calculation for the finding of Easter. Honour'd Sir, I have a Swedish Coyn, or rather Square Copper Plate, 9 inches broad, and 9 and a half long, which is much like the Roman Æs grave, and was currant there so lately as An. 1679. (tho now they are not to be met with) It has at each corner the Impression of a Crown, under which is the Year, and round it this Inscription, CAROLUS XI. D. G. SVE. GOT. WAN. REX. and in the middle of the Plate in a Circle 2 DALER. SÖH. Mjt. The other side of the Plate is without any Inscription. The Treatise you mentioned concerning a Coyn of mine, inserted in the late Edition of the Britannia, is, I presume, upon the Runic Annulet of the God Thor, of which I have the Learned Readings of two very great Men, my Lord Bishop of Carlisle and Dr Hicks: And as the Antient Heathens inscribed the Name and Effigies of their reputed Deity upon that Piece, so several of the Modern Christian Princes of those Northern Countrys, have inscribed the Nomen Tetragrammaton of our Almighty Jehovah on some of their Moneys: I have seen Svenska marc of Charles the 9th with it, surrounded with rays of Glory in the midst of the Area on the Reverse, and a Mark, ½ Mark, and a 2 Mark piece all of the famous Gustavus Adolphus, with the like Characters above the Kings Head. The Learned and Ingenious Richard Thornton Esq; upon reading Dr Wallis's Letter to Sir John Blencowe, one of his then Majesty's Justices of the Court of Common Pleas, Please, concerning the observation of Easter, registered in the Phil. Trans. 240, made this Calculation. Rightly to understand the Rule in our Common Prayer Books for finding Easter. Note, 1. That the 21st of March, in all but Leap-years, and in Leap years the 20th of March, was, at the time of the Council of Nice, when this Rule was made, the Vernal Equinox: Consequently, 2. That the 20th of March in Leap-years is the same as the 21st of March in common years. 3. That the Full Moon meant in this Rule is not to be found in our Almanacks, but by the Calendar of our Common Prayer Books, where, in the first Column the Golden Number of every year is placed over against the day of the New Moon in every month of the year. 4. That the fourteenth day, including the first day of the Moon, is the Full Moon, and not the fifteenth, as Dr Wallis would have it in his Letter. VII. An Account of an Experiment made at a Meeting of the Royal Society at Gresham College, upon the Propagation of Sound in Condensed Air. Together with a Repetition of the same in the open Field, by Mr F. Hauksbee. A Bell being included in a Brass Recipient, and plac'd at one end of a Room, about 50 yards in length: At the other end of which stood some Gentlemen to observe the sound; which before any Air was intruded, the Bell upon shaking was heard at that distance, tho' not without diligent attention. Upon the Intrusion of one Atmosphere (begging leave to call it so) the Bell being shaken as before, the sound was very sensibly augmented;