( 451) 
gs, (which encloses also the packing of g,), so that the gas can 
always stream freely from gjo to fy), for which purpose also grooves 
have been cut in the tube 7. The stem gs), is usually also screwed 
back a few turns and the valve may still, without being hindered 
by the peg, be raised so far by the mercury rising suddenly that it 
closes the opening 44). 
It will be remarked that the connection between the several parts 
of g and f is a little more complicated than is required; this will 
also appear to be the case for g itself, which is explained by the 
remark at the end of §1; the detailed drawing may be useful for 
those who wish to change a CAILLETET-pump into a compressor of 
the Leiden pattern. 
The nut g, (Pl. VI fig. 2) presses g,, closely against 95. In 
the same way as CAILLETET we use the pointed screw g;, to let 
mercury flow out into the tube g,, from the mercury reservoir g5, 
through the hole g;3 and the opening g;,, from there it is received 
in the exhaust-chamber and from there again in the pump cylinder, 
provided these spaces are under no pressure. This screw-cock is 
only opened at the commencement or in the case of leakage. Gene- 
rally the pump sucks gas through g;, from the cavity y52 and the 
chamber gg (sce Pl. II). 
The latter (comp. § 2 €. 3) is made from a gun barrel, provided 
with the necessary steel mountings (see Pl. VI fig. 2). The 
gas is admitted into it by the tube gj. On the joint g-, connected 
with it, several conducting tubes (1, II, and III) with nuts and 
packing can be screwed. 
At the lower end this chamber is provided with a cock 90; to 
let out any mercury that might have run over. The upward 
bent tube g,,, which can be screwed off, must give a tight joint 
by a mercury layer. Even if a small quantity of mercury begins 
to overflow into the tube by insufficient closure of the valves the 
contact gg, gives warning immediately (comp. § 2 ©), while the 
contact gg, indicates that more mercury has run over than was 
contained in the pump cylinder above the suction-valve (see Pl. 
ID, and hence that something is wrong with the compression: 
tube C'p. 
z. The transference of the compressed gas. The compressed gas can 
escape (see Pl. III) from the reservoir through the conducting tubes 
k and 4. If this is done slowly, very little mercury usually will be 
carried along. Therefore the cocks are always opened very carefully 
and except in urgent cases the gas is let out as slowly as it is 
admitted by the regular working of the pump. 
