(4S ) 
IV, Part of a Letter from M^e\\^][\mriJ^et\nm^ 
to Dr, Sloane § accomfanywg his Ohfer'^ 
*vations of the Height of the Mercury in the 
Barometer^ Kains^ Winds ^ Scc. for the Year 
JF any Explication be needful to theft TablesJ refer yoa 
io Philcf. Tranf Numb. 137. 
_ The Quantity of Rains which fell through my Tuooe! 
laft Year was iixjx Pounds : which exceeds the Quari' 
tity of — -97. that being but 77,60 Pounds. 
1 find Foggy Weather makes the Mercury rift^ as well 
as the Nortii-Wind; as may be obferved in the Table, 
ia the Month of Decemher^ at which time the Mercury 
was very high, although the Wind was in the Sou- 
therly Points. I fubmit it, whether the Caufe be 
not the mcxtd^k of the weight of the Atmofphere, 
by an Addition of thofe Vapours of which the 
Fog conlifts, which are manifeftly as heavy as the Air^ 
becaufe they fwim in it without afending ? Theft filling 
up many of the Vacuities of the Air, without extruding 
much the parts of Air (as I judge Clouds do) do add 
confiderably to the Weight of the Atmofphere, and fo 
caufe the Mercury to aftend. But this I leave to 
better Judgments. 
It may not perhaps be ungrateful to you to obftrve, 
that the greateft Range I have ever cbftrved the Mercu* 
ly to hav e, is no more than x,i2 Inches • it being here 
never higher than 3040, nor lower than 28,28 inches, 
the lovveft it ever was, within my Obfervations, was 
G Jane- 
