a pretty capaceous Bolt-head AB, with
a small stem about two foot and a half long DC; upon the end of this D
I put on a small bended Glass, or brazen _syphon_ DEF (open at D, E and
F, but to be closed with cement at F and E, as occasion serves) whose
stem F should be about six or eight inches long, but the bore of it not
above half an inch diameter, and very even; these I fix very strongly
together by the help of very hard Cement, and then fit the whole Glass
ABCDEF into a long Board, or Frame, in such manner, that almost half
the head AB may lye buried in a concave Hemisphere cut into the Board
RS; then I place it so on the Board RS, as is exprest in the first
figure of the first Scheme; and fix it very firm and steady in that
posture, so as that the weight of the _Mercury_ that is afterwards to
be put into it, may not in the least shake or stir it; then drawing a
line XY on the Frame RT, so that it may divide the ball into two equal
parts, or that it may pass, as 'twere, through the center of the ball.
I begin from that, and divide all the rest of the Board towards UT into
inches, and the inches between the 25 and the end E (which need not be
above two or three and thirty inches distant from the line XY) I
subdivide into Decimals; then stopping the end F with soft Cement, or
soft Wax, I invert the Frame, placing the head downwards, and the
Orifice E upwards; and by it, with a small Funnel, I fill the whole
Glass with Quicksilver; then by stopping the small Orifice E with my
finger, I oftentimes erect and invert the whole Glass and Frame, and
thereby free the Quicksilver and Glass from all the bubbles or parcels
of lurking Air; then inverting it as before, I fill it top full with
clear and well strain'd Quicksilver, and having made ready a small ball
of pretty hard Cement, by heat made very soft, I press it into the hole
E, and thereby stop it very fast; and to secure this Cement from flying
out afterward, I bind over it a piece of Leather, that is spread over
in the inside with Cement, and wound about it while the Cement is hot:
Having thus softned it, I gently erect again the Glass after this
manner: I first let the Frame down edge-wayes, till the edge RV touch
the Floor, or ly horizontal; and then in that edging posture raise the
end RS; this I do, that if there chance to be any Air hidden