E 11 3 
SECT. V. 
Of the Ombrometer . 
TT'HIS Machine confifts of a tin Funnel y whofe 
^ Surface is an Inch fquare, a flat Board, and a 
glafs Tube let into the Middle of it in a Groove 
(the Length and Breadth of both Board and Tube 
being ad Libitum), and an Index. My Board 
is about three Feet long, to anfwer the Height 
of the Rails that go round the Top of my Houfe, 
to one of which it is hung, clear of any Obftacle 
to prevent the free Fall of the Rain, with four 
little Staples that Aide over as many Tenter-hooks. 
The Bore of my Tube is about half an Inch; which, 
at a Medium, is the beft Size, a larger Bore obliging 
you to make your Graduation the more contra&ed, 
and, confequently, the lefs plain and accurate ; and 
a leller not permitting you to return the Water out of 
the Tube when full, without the Adhefion of a great 
deal to its Sides 5 which, when you have placed the 
Tube in its perpendicular Situation, fubfides, and 
fometimes fills up x? of an Inch; which, without 
Care, mud neceflarily make great Miftakes in the 
Diary . The Method of graduating the Board is this : 
I had a Vefiel of Tin made, whofe Contents were 
cxadly a Cubic Inch. With this Vefiel,. filled with 
Water exadly to its Surface, I frequently gauged the 
Tube, till, by repeated Trials, I had found the Height 
to which a Cubic Inch of Water would rife in it. 
The Space anfwering to this on the Board I had gra- 
duated into 3 2 equal Parts, and took the fame Me- 
thod with the reft of the Tube, till in the fame man- 
ner 
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