Ing at one time lower than at another, is the effe£l of two 
contrary Winds blowing from the place where the Barometer 
ftands ; whereby the Air of that place is carried both wais 
from it, and confequently the incumbent Cylinder of Air is 
diminifhed, and accordingly the Mercury finks ; as for in- 
ftance , if in the Germm Ocean it fhould blow a gale 
of Wefterly Wind , and at the iame time an faiter- 
ly Wind in the Irijh Sea ; or if in ¥rance it fhould blow 
a Southerly Wind, and in Scotland a Northern ; it muft be 
granted me that that part of the Atmofphere impendent over 
£;2g;/^W, would thereby be exhaurted and attenuated, and 
the Mercury would fubfide, and the Vapours which before 
floated in thofe parts of the Air of equal Gravity with them- 
lelves, would fink to the Earth. 
2. Why m Serene good fetled Weather the Mercury is gene* 
rally high ? To this I anfwer , That the greater hight of the 
Barometer^ is occafioned by two contrary Winds blowing ^t?- 
wards the place of Obfervation, whereby the Air of other 
places is brought thither and accumulated ; fb that the in- 
cumbent Gyhnder of Air being encreafed both in hight and 
weight, the ikfc/w^ prtffed thereby muit needs rife and 
ftand high, as long as the Winds continue fb to blow ; and 
then the Air being ipecifically heavier, the Vapours are better 
kept fiifpended,{b that they have no inclination to Prsscipitate 
and fall down in drops, which is the reafbn of the Serene 
' good Weater, which attends the greater hights of the Mer* 
cury. 
3 . Why upon very great Winds or Storms though accompanied 
with no Rain^ the Mercury {inks lowefi of all, with relation to 
the point of the Qomfafs upon which the Wind blows. This is 
caufed by the very rapid motion of the ^/>in thefe Storms ; 
for the Tra£t or Region of the Earths Surface wherein thefe 
Winds rage, not extending all round the Globe, that flag- 
nant Air which is left behind, as likewife that on the fides, 
cannot come in fb faft as to fupply the Evacuation made by 
fo fwift a Current, C) that the Air muft necelTarily be atte- 
nu-« 
