[ * 5 « ] 
the remainder of the Mercury , and it muft rife a 
little. 
Or fuch violent jarring puts the Mercury in a lateral 
and upward Motion, (for downward it cannot go) 
which takes off its Gravity, as the Winds leffen the 
Preffure of the Air j therefore it muft rife a little. 
But then it is obfervable alfo, that if the Mercury 
was in a (landing Condition, or falling,’ fuch rifing. as 
above, will in a Minute come to the fame Place again ; 
and even when the Mercury is in a rifing Condition, 
it will, in that Space of Time, fall a little part of that 
it rofe by fuch rapping. 
This Barometer has the Corufcations , as they were 
obferved in Mr. Patrick's pendant one 5 for by rap- 
ping the Cafe with the Finger in a dark place, it will 
emit feverai bright Flafhes, along the empty part of 
the Tube . 
This I take to be an Argument that the Vacuum is 
very pure, and the Mercury truly purged. 
I (hall not need to fay any more, having doubtlefs 
already defcended to Trifles ; only 1 would add, which 
I can with Truth and without Vanity affirm, that in 
all the Affairs of Husbandry, but efpecially in Harveft, 
it hasfeldom failed me inforetelling the Weather fo 
well, as to be very advantageous to me for nine Years 
together 5 and fo pleafing and fatisfa&ory at other 
times, that they who never had one, cannot know 
the want of it i and thofe only who have ufed it, are 
able to know its Ufefulnefs 5 and that I could not with- 
out fome Reftraint, and more Reludtancy, be without 
one of thefe Barometers . 
