Page:Philosophical Transactions - Volume 024.djvu/431

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(1902)

Pleas, concerning the observation of Easter, registred 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;two

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