LEVEL. 
frame, called a Y, screwed to the end of the 
arm C ; it supports in its forked termina- 
tion one end of the telescope K, of which 
the other end rests in a Y, (lettered N), 
similar to H, but which can be raised or 
lowered, by means of a screw having a 
Iniiled head ; as seen at y. Tlie spirit level 
L is fixed to the telescope by two screws 
at its ends, whereby it can be brought into 
exact adjustment with the culmination of 
the telescope. 
The level, which is the essential part of 
the instrument, has been already describ- 
ed; but it is proper to add, that the 
ends of the tube containing the alcohol, 
when made of glass, should be hermetically 
sealed at its ends, which should then be 
cased in brass. Mr. Ramsden preferred a 
very slight convexity in the tube ; consider- 
ing it best adapted for shewing the most 
trifling deviation from a perfect level, and 
causing the bubble to become more ac- 
curately centrical. With respect to the 
telescope, it is similar to those generally 
fitted to theodolites, &c. and has been de- 
sci ibed in the preceding part of this article. 
It is laid on in the two Y pieces, and kept 
in by two curved pieces of brass. In 
figure h is the achromatic object glass, 
fixed within the end of a tube, sliding with- 
in the external cylinder of the telescope, 
and moved very gradually by a rack and 
pinion on the mill headed nut i : the dis- 
tance of the glass h from the eye-piece, is 
thereby adjusted to a suitable focus. 
The eye-piece K contains two lenses, 
sliding in a tube fixed to the telescope, for 
adjusting them to a distinct vision of the 
cross wires, or hairs, which are held in a 
proper state of tension in the frame t, and 
regulated to the axis, dr line of sight, by 
four minute screws passing through the 
outside of the telescope. 
We have before shown how the four 
screws act upon the two parallel plates, a a 
and c e, while the axis b can be set very 
nearly perpendicular ; then by the screw 
'll the telescope can be set very nearly le- 
vel. To turn the telescope about hori- 
zontally upon its axis I, a screw »i, works 
in a fixed collar r; its nut p,, is fasten- 
ed upon an arm which projects from a 
clamp g, embracing a collar upon the axis 
I, and is tightened by a screw r; which 
being unscrewed the clamp springs open, 
and the telescope, together with the level, 
moves round with freedom upon the axis I, 
according to the pleasure of the operator. 
AVhen the screw r is tightened, the clamp 
holds the telescope fast, but admits of a 
slight movement, either way, when acted 
upon by the mill-headed screw m. 
Our readers will readily perceive the 
simplicity of this level, beyond any others 
in use; and will lament the demise of a 
gentleman who, to profound theory, added 
the most ingenious and skilful practice. 
Where a very long, and continued range 
of brickwork is to be raised, it is often ad- 
visable to use a water level, made by laying 
a ridge of mortar along the centre of the 
wall, and opening a very narrow channel 
throughout its centre longitudinally^ so as 
to form a kind of trough, let the ends be 
stopped, and the trough be filled with water, 
as far as it will flow. The surface of the 
water will give a true horizontal level; 
which if continued for miles would conform 
exactly to the curvature of our globe. To 
continue the level along the rest of the 
trough, stop it at the place where the 
water reached, and raising the adjacent 
part with more mortar, let the trough of 
the superior level be filled, and thus in suc- 
cession. The difference between the end 
of one trough, and the beginning of another 
will shew the respective levels ; from which 
parallels may be set off at any height above 
by plumb lines of equal length. This mode 
is often practised in large works, such as 
fortifications, and when strata of masonry 
are to be regularly disposed ; also to pre- 
vent those irregular breaks, and partial 
connections, that are almost inevitable 
w'here small sallows, or triangular levels, 
with plumb weights are in use. 
When no instrument can be obtained, 
and where it is not easy to draw an exact 
level by the foregoing means, take the hose 
of an engine, and having fixed one end at 
the spot whose level is lo be sought, (on 
any opposite bank for instance,) carry the 
other end to the place w'here the corres- 
ponding height is to be established. Fill 
the hose with water until it ceases to re- 
quire raising at the further end. When 
both ends show full to the brim, and that 
the water is retained at both, then they are 
on the same level : for it is a maxim in 
Hydrostatics (which see), that water, or. 
indeed, any fluid heavier than atmospheric 
air, will, when at liberty, always find its 
own level. 
Where a succession of contiguous levels 
are^ wanted, it will often be found con- 
venient to use a small leaden pipe, of about 
half an inch bore, which should be applied 
as above described; or even a common 
