( lp'02 > 
Plear, concerning the obfcrvation of F.afur^ rcgiftrcd ia 
the PhL Irafjf. 240. made this Calculation. 
Rightly to und^rftand the R.ule in oiir Common* 
Prayer Books for finding EaJJer. Note, 
1. Thst the 21ft; of March, in all bin Leap-years,* and 
in Leap-years the 20th of March^ war, at the time 
of the O uncil of Nice, when this EVnlc was made, 
the Vernal Equinox : Conft-quenrly, 
2. That the :oth March in Leap-years is the fimc as 
the 2ift of March in common years. 
5. That the Full Moon meant in this Rule is not to be 
fxDUnd in our Almanacks, but by the Calendar of 
our Common Prayer Books, where, in the firft Co* 
lumn the Golden Number of every year is placed 
over againft the day of the New Moon in every 
nsonth of the year, 
4. That the fourteenth day, including the firft day of 
the Moon, is the Full Moon, and not the fifteenth, 
as Dr WalUs would have it in his Letter. 
VII'. Jn Jccount of an Experiment made at a Meeting of 
the Q{oyal Society at Grefliatn College, up9n the 
Propagation of Sound in Condenfed Air. Together 
with a ^^petition of the fame in the open Field^ by 
Mr F. Hauksbee. 
A Bell being included in a BraG Recipient, and plac'd 
at one end of a Room, about 5c yards in length : 
At the other end of which ftood fome Gentlemen to ob- 
ferve the found 5 which before any Air was intruded, 
the Bell upon fhaking was heard at that diftance, thonot 
without diligent attention. Upon the Intrufion of one 
Atmofphere (begging leave to csll ii fo) the Bell bemg 
flaaken as before, the found was very fenfibly augmented 5 
two 
