666 Col. roy’s Experiments for 
rnately in the focket itfelf, fitted it fo exactly, as to fuffer 
no water to pafs. The focket being inferted into the 
aperture at the bottom of the veffel, was firmly foldered 
to it for the reception of the tube, which was fo ground 
as to reach a full inch and a half below the furface of 
the brafs. It could not defcend farther, the ground parts 
in both being of the figure of the fruftum of an inverted 
cone. From the view in the plate it will appear, that un- 
derneath the veffel, a feparate Hand was placed, in order 
to fupport the iron cittern containing the quickfilver. 
The diameter of the cittern was fuch, that its ttand being 
occafionally moved, fo as to bring one fide of it clofe to 
the ground part of the tube, the other fide projected be- 
yond the bottom of the veffel; and confequently per- 
mitted the rod of a float, retting on the furface of the 
quickfilver, to rife freely and parallel to the axis of the 
tube. The rod was of deal, f^th of an inch fquare, car- 
rying on its top a fcale, whofe zero lay in the lower fur- 
face of the float, and whereof the fix uppermott inches, 
from 2,8 to 34, were divided into zoths. 
That the whole column of quickfilver might alter- 
nately be covered with the freezing mixture and water 
of different temperatures, and yet permit its furface to 
be feen, two eyes of plate glafs were fcrewed into fockets, 
foldered for that purpofe oppofite to each other, near the 
top 
