IX. A Letter from Mr. Halley of June the yth. 
P7 concerning the Torricellian Experiment 
tryed on the top of Snowdon-hill and the fnc- 
cefs of it. 
L 
AST Whitfon^mek by the favour of Mr. Davit^ 
. . a good Friend of Dr. Trancred Rohinfon's^ I had 
the opportunity of feeing what I pleafed in North Wales^ 
and was on Wednefday May 26, on the top of Snovodon 
where I tried the Torricellian Experiment with all the 
fatisfadion I could wifti for ,- the Air continued both 
before and after in the fame ftate as I got it verified 
by Mr. Davis's (landing Barometer at Llannerch in Den- 
ly-Jhire^ about Miles Eaft from Snowdon where it 
was Obferved as follows. 
h ' Inch. ' 
May X5 8 15- 29 7 
h 
8 
IS 
lO 
s 
z6 
8 
16 Morn. 
II 
00 Mora 
00 Aft. 
6 
00 
9 
30 
17 
6 
00 Morn. 
10 
00 
3 
30 Aft. 
6 
I J Aft. 
5 
00 Aft. 
10 
00 
^9 8 
29 8 
74 
^9 71 
29 7 
Z9 7 
ip 7j 
29 8 
29 8 
££4»mA is about a Mi!e and an half above the 
Towa ot St,.Afafh, about 6 Mile from the Mouth of the 
River 
