204 A, D. Bache on Guif Stream Explorations. 
to one tenth of a square inch. The cylinder is bored out a little 
larger than the plunger except for about a fourth of an inch near 
each end at C and D where both are accurately fitted. To the 
branch E a pipe connects, communicating with the hydraulic — 
cylinder and leading the water into the centre of the gauge which 
it reaches after passing through the chamber F filled with sponge 
to prevent any impurities in the water from reaching the plunger. 
The upper end of the plunger connects by a wire W, to a spring 
as shown in the sketch at G, so constructed.as to indicate pres 
sure from 0 to 450 tbs., the spring being so strong that 450 
produce a movement of the plunger equal to three-eighths of an 
inch. It is evident that as the difference in area of the en 
the plunger is one-tenth of an inch, one hundred pounds pressure 
from the water on this surface, as indicated by the balance, would 
equal a pressure of water of 1000 tbs. per inch, or 
ap 
times as great as that indicated by the balance throughout 1!8 
scale. The only difficulty in the use of the gauge is that of fit 
ting the plunger to the cylinder so that while it Is perfectly free 
to move it is also perfectly water tight. This difficulty however 
has been overcome, and much advantage was also derived irom 
Mr. Batchelder’s suggestion for supplying the wear of the Ke 
ger and cylinder by depositing brass on the plunger throug 
galvanic process.” : : 
Connected with this gauge by a pipe is a strong wn 
eT, 
the thermometer was placed, the opening being firmly dot Y 
ascrew plug. This second cylinder was immersed in pag 
oved, the 
effect upon the thermometer; at 1500 ibs. the effect 15 fee eo 
one degree; and from 1500 to 4000 tbs. per square") 14 
effect is to diminish the readings, the maximum ee ©" 
Seven degrees, : i 
e diagram exhibits the law of diminution by increas? 
tion to be applied varies with the depth. F 
correction t ae a ie 
or 5 it is only four tenths of a degree Fahrenheit ieee at the 
same de 
pressure, and the depth corresponding to different pe - 
age For thermometer No. 10, it is one @fa" 
a | . 
