t 1 57 3 
many Days together $' you may reafonably expert a fair 
Seafon for as long a time as it was rifing, unlefs feme 
Gales of Wind intervene, and efpecially the S W by 
S. or thereabouts. 
7. When the Mercury rifes very faft, or falls very 
faft, neither the fair nor foul Weather it forebodes 
will continue long. 
8 . Without knowing how the Mwcury has flood 
fome little time before, .a true Judgment cannot be 
given at all times : For fuppofe I find it in a riftng Con- 
dition, 1 am apt to think it will be fair 5 but if it had 
been higher fome Hours ago, and fell, there muft hap- 
pen a Shower. 
[A.] What I promifed in ‘Page 2f2. to explain. 
Was, 
Why the Mercury in the ‘Diagonal Barometer (if 
it be for fair Weather) on rapping the Cafe feveral 
times, which jars and makes the Tube tremble, will 
rife at every Stroke for feveral Strokes together, and 
in all fometimes a 10th of an Inch, or more, in the 
perpendicular 5 may, I prefume, be thus accounted 
for : 
1. There is a Cohefion of the Mercury to the Tube*, 
which hinders its rifing, and fuch rapping releafes 
that. 
2. But it is obfervable, that it will rife a little at 
all times, even when it is in a {landing or even in a 
falling Condition* This may be accounted for thus : 
The Mercury and At mo fy her e are in an Equilibria , 
and rapping ftarts and raifes the Mercury a little in a 
boiling manner, efpecially the upper Surface of it, 
which is feen to leap, or be in a fwimming Fofture* 
then the Preffure of the Atmofyhere over- balances 
Kk 2 the 
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