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cut and fit precisely in the small ring ¢,;. A little below the washer 
case the screw-thread must end in a cylindrical boring corresponding 
with the part of %33 projecting outside the packing. The packing 
itself is pressed into a conical space and care must be taken that 
new layers of leather (or cork) are always added in time, before 
the packing-compressor 7, is screwed too far down by the nut #2. On 
placing the cock in the apparatus, care must be taken that the 
point is directed towards that side, where the removal of the pack- 
ing, which these cocks especially permit, could offer difficulties. 
To show that the position of the cock may not be altered the handle 
is taken away from the head of the pin. 
As usual the capillary 7 is fastened into the overpipes with 
screw-threads and marine-glue. 
When the cock 7, is open the boring /, communicates with the 
cock 7. In the boring 75; of this cock is a filter consisting of 
closely packed platinum-wires 7,,, enclosed in a small case with 
sieve-shaped bottom ús and with a rim and washer ús resting 
on the cock itself. The satisfactory working of the filter depends 
on the pump being thoroughly cleaned, an operation which is rarely 
necessary with my construction, and which therefore can be done 
with the utmost care, 
With one of the cocks i we regulate, with the other we shut 
entirely, a thing which should not be forgotten if the work is — 
stopped for a moment. Moreover these two cocks are required for 
removing the capillary from the pump when necessary without inter- 
rupting the work. If everything goes well we can see the capillary 
moving regularly between two positions (like a Bourdon spring) 
under the influence of the alternating pressure. 
The boring #, communicates with the boring #4 in the pump 
body. To adjust the cock # to this so that the packing can be 
tightened while the cock remains perfectly stationary (which the 
space at our disposal renders necessary in view of the capil- 
lary connected with it) a cylinder shaped lengthening piece #9 with 
flange is forged on #,. It is fastened in the boring e,. by means 
of a bored conical joint with a thread #,, which is in two pieces, 
held together by pegs. 
In the boring e‚‚ an ebonite cap eg with packing is fastened, so 
that, when as much mercury as possible has run through i, a 
layer remains to assist the closure of e‚ in ¢,. 
7. Forcing-valve with accessories. The steel pressure-valve (PL. V 
fig. 1) rests on the support e, which is serewed in the upper-end 
