for water works purposes than
any other, with the possible exception of the Cornish.

* * * * *

IMPROVED GUN PRESSURE GAUGE.

The following description of the construction and mode of action is by
Thomas Shaw, M.E., Philadelphia, the inventor.

[Illustration: IMPROVED GUN PRESSURE GAUGE.]

Fig. 1 represents the gauge secured to small ordnance, the gun shown in
cross section. Fig. 2 represents face view of the gauge and indicator,
exposing a vertical section through the hydraulic portion of the gauge,
on line 3 and 4 of Fig. 1. The same principles of reduction of high
pressure are used in this gauge as in Shaw's hydraulic gauge. It will be
observed that a solid steel piston, E, in the cylinder, A, is provided
with a plunger on its under side, which comes in contact with an elastic
packing, D; the plunger may stand as 1 to A 1,000, or as 1 to A 100, in
point of area of exposed surface, as compared with the large piston head,
as desired. Assuming the proportions to be 1 to A 1,000, the 1,000 lb.
pressure on the plunger means only 1 lb. pressure in the fluid chamber,
above piston head, E, and this greatly reduced pressure is now
susceptible of measurement by any of the ordinary light pressure
instruments for measuring pressures. All the passage ways connecting to
dial gauge, R, with the fluid chamber above piston, E, are filled solid
with fluid, permitting no air spaces that can be avoided. The steel plug,
L, that forms a passage way between the fluid chamber and the dial gauge,
is provided on one side with a small screw hydraulic pump, with a
reservoir supply of fluid. This part is shown in longitudinal section;
the steel plunger, I, is firmly secured to wheel, F, the long hub, H, of
which is provided with a screw thread on its inner side, which thread
screws upon the exterior of pump barrel, K. After first filling the
interior of the pump barrel with fluid, the said hub is screwed upon the
pump barrel, causing the plunger, I, to force the fluid into the fluid
chamber and passage way leading to the dial gauge, causing the hand or
pointer to move to any predetermined pressure on dial, in advance of
pressure applied in the high pressure chamber at D. The purpose
accomplished in this act is to give the least possible movement of the
pointer to record any maximum pressure, as, for example, assuming that
20,000 lb. was the expected pressure from any one explosive, then the
pointer, b