Royal Society. 313 
the diftances between the claps and the ecchoes and the following 
claps were equal 5 and tho' it be very difficult to be exact herein, 
yet he could come within lome few yards of the place he louG^t for, 
thus 5 he oblerved two places in which he could but juft dilcover 
where he was too near, and where he was too far off, and from the 
midway betwixt them he mealured to the wall, which meafure 
doubled was the ipace that the found moved in half a fecond. 
Here follow the number of Engljp feef which a found moved 
in one fecond of time at feveral trials. 
Triciis 
• en 1 
IViiJs 
j-eet 
1292 
1 Trials 
Feer 
1278 
1 
11)6 
5 
9 
z 
17071 
6 
1378 
10 
129c 
3 
152^; 
7 
1292 
11 
1200 
4 
1150; 
^ 
ri85 
Merfenmis mentions an experiment wherein he found the mo- 
tion of a found to be 14.74 feet in a fecond of tm^.e 3 the aca- 
demy del Cimento caufed fix harquebuffes and fix chambers to be 
fired one after another at the diibnce of 5759 EfigUJh feet and 
from the flafh to the arrival of each report was 5 fcconds, and re- 
Deatin? the experiment at the midway, the motion wasexaaiy in 
half the time ; and Mr. ^oyle obfervedthat the motion of lound 
paffes above 400 yards in a fecond; when the firft trial was made 
there was fome wind ftirnng, tho' not much; the 2d, 3d and 6":h 
were made in a calm morning ; in the 8th the eccho was returned 
from a wall at 395 yards diilance m two feconds; and in the 9th 
and I oth at 213 and 215 yatds diftance in one iecond ; tne 4rh 
was made at one end of St. yohris. cloifter m O^ord which is 
104 feet 7 inches Ion?, where the found was reflected i r times 
in two feconds, and' the 5th on the north fide of ]<le-w College 
cloiiter, which is i6q feet 8 inches long, where there were 7 1 ec- 
choes in two feconds; by fome of the experiments he made, he 
was inclmed to think th;it the found moved quicker w-jicn it was 
calm, than in a wind, even when the lound moved half way with 
the wind, and that it moves fwifter at fii/l than afrei-wards; 
there is leldom any eccho where there is not fome vvall, wood, 
bank or fuch like directly oppofite, that may reflecl the louml to 
the perlon that makes it; but in St. yobns grove if you Itand 
near the gate le.idmgfrom ibe College to the grove and clap, tne 
eccho will return to you from the ball-court, tho a line drawn 
from YOU to the ball-court be not perpendicular to the wall tiicre, 
YoL. Hi. R ^ ^''' 
