202 FHILOSOPHICAL TRANSACTIONS. [aNNO 1705. 



Concerning some Swedish Coins ; and a Calculation for Ending Easter. By 

 Mr, Ralph Thoresby, F.R.S. N° 297, p. IQOI. 



I have a Swedish coin, or rather square copper plate, 9 inches broad, and 9 

 and a half long, which is much like the Roman JEs grave, and was current 

 there so lately as An. 1679, though 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. Soih. Mijt. The other side of the 

 plate has no inscription. 



The learned Richard Thornton, Esq. on reading Dr. Wallis*s letter to Sir 

 John Blencowe, concerning the observation of Easter, in Phil. Trans. N° 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 2ist of March in common years. 3. That the 

 full moon meant in this rule is not to be found in our almanacs, but t)y 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 I4th day, including the 1st day of the 

 fnoon, is the full moon, and not the 15th, as Dr. Wallis would have it in 

 his letter. 



An Experiment, made at Gresham College^ on the Propagation of Sound in 

 condensed Air : with a Repetition of the same in the open Field. By Mr, 

 F. Haukshee. N° 297, p. 1902. 



A bell being included in a brass recipient, and placed at one end of a room 

 about 50 yards long, at the other end of which stood some gentlemen to 

 observe the sound ; before any air was intruded, the bell on shaking was heard 

 at that distance, though not without diligent attention. On the intrusion of 

 one atmosphere of air, the bell being shaken as before, the sound was very 

 sensibly augmented ; two atmospheres being impelled, and the bell made to 

 ring, a considerable improvement of the sound was then manifest. But on 

 the intrusion of the 3d, 4th, and 5th atmospheres, the bell being made to 

 strike, the sound seemed not to be propagated proportionably to the first and 



