IMPROVEMENTS IN THE CONSTRUCTION OF LEVELS APPLICABLE TO LEVELLING, SURVEYING, ASTRONOMICAL, NAUTICAL, AND OTHER INSTRUMENTS OR PURPOSES TO WHICH LEVELS ARE APPLICABLE
Year: 1863

page_text: PROVISIONAL SPECIFICATION left by John Phillips at the Office of
the Commissioners of Patents, with his Petition, on the 23rd Sep-
tember 1863.
I, JOHN PHILLIPS, of Tollington Road, Holloway, in the County of Middle-
sex, Civil Engineer, do hereby declare the nature of the Invention for
"IMPROVEMENTS IN THE CONSTRUCTION OF LEVELS APPLICABLE TO LEVELLING,
SURVEYING, ASTRONOMICAL, NAUTICAL, AND OTHER INSTRUMENTS OR PURPOSES TO
WHICH LEVELS ARE APPLICABLE," to be as follows:-
This Invention has for its object improvements in the construction of levels,
whereby they indicate very accurately the true horizon and vertical angles of
inclination which it is desired to ascertain.
The levels constructed according to the first part of my improvements are
particularly applicable to levelling, surveying, astronomical, nautical, and other
instruments, and also other purposes to which levels are applicable, and in
which instruments and purposes great accuracy is required to ascertain the
true direction of the horizon, and of vertical angles of deviation therefrom.
Levels constructed according to my Invention consist of two or more vertical
tubes, chambers, or passages rising from a channel of communication between
them, such tubes, chambers, or passages containing a fluid (by preference

page_text: mercury) which rises partly up the vertical tubes or passages, so as to indicate
a uniform or corresponding level in each.
And in order that this part of my Invention may be clearly understood, I
will describe a convenient form of instrument and the manner of constructing
the same, which may be employed in carrying out this part of my Invention.
I take a rectangular piece of stout plate glass of suitable length and depth for
the size of the intended level, and near to or along the lower edge thereof
I drill or otherwise form a channel of communication, and near to each
end I drill or otherwise form a vertical tube or chamber which rises
from the channel of communication to near the upper edge of the plate of
glass, other vertical tubes or chambers intermediate of the two end tubes or
chambers may be formed if desired. All the inlets to these tubes, chambers,
or passages being permanently closed, except one, the whole of them are then
filled with a fluid (by preference, mercury), so as to drive out or exclude
atmospheric air, then, a certain quantity of the fluid being withdrawn and the
outlet hermetically sealed, vacuums will be formed in the spaces left above the
mercury or other fluid, the top surface of the mercury or other fluid in
the vertical tubes or chambers will thereby be truly horizontal or level with
each other. The plate containing the vacuum tubes or chambers thus formed
may be encased in a sheath of metal or other suitable material for protection,
the sheath having slots or openings cut therein to correspond with the vertical
tubes or columns, so as to exhibit them on each side of the instrument. There
is an arm at each end of the sheath, which arms pass over vertical pins or
studs fixed upon a stand or base plate; the upper ends of these pins or studs
have screw threads cut thereon and carry screw nuts above and below the arms
to adjust the position thereof, as is well understood in the mounting and adjust-
ment of ordinary spirit levels. The edges of the slots in the plate opposite
cach tube or column are marked with suitable scales, which indicate not only
when the instrument is truly horizontal, but also the various degrees of vertical
inclination from the horizon, or from the base line of the instrument.
The form of and mode of constructing levelling instruments in accordance
with the character of this part of my Invention may be greatly varied, and I
would have it understood that I do not confine myself to the construction and
arrangement of instrument above described, so long as the principal features
of my Invention be retained. In place of having two or more vertical tubes
or chambers rising from a channel of communication a simple chamber may
be employed, containing mercury or other fluid with a vacuum formed above
the top surface thereof, as previously described, suitable scales being engraved

page_text: or marked at or near to the ends of such chamber to indicate the true level
or vertical angles therefrom as before described. It will be evident that
vacuum levels constructed as above described may be employed in combination
with levelling, surveying, astronomical, nautical, and other instruments, to which
ordinary levels are applicable, and my improved level may be advantageously
employed in combination with the beams of balances to indicate the equilibrium
thereof, and to other purposes where levels are required.