46 THE ATLANTIC. [ CHAP. 1. 
known form of the lecture apparatus known as “ Hofmann’s 
tubes.” It consists of two tubes, A and B, united at their 
; lower extremities by a short tube, C, 
which connects them at the same 
time, by means of the tube D, with 
the reservoir E. At their upper ex- 
tremities, A and B terminate in cap- 
illary tubes provided with stop-cocks, 
F, F. Communication with the res- 
ervoir can be made or interrupted by 
the stop-cock G. One of the tubes, 
A, is provided with two platinum 
electrodes; the other, B, has but one. 
Bent delivery-tubes, not shown in 
the drawing, fit on the tubes above 
the stop-cocks F, F. When about to 
be used, all the stop-cocks are opened, 
and dilute sulphuric acid poured in 
SS OG 
SSS S SJ through the reservoir until it has 
Fia. 8.—Gas-generating Apparatus. 
j eliminated all air, and is running 
out at the delivery-tubes. The stop-cock G is now shut, and 
the battery connected as circumstances may require, either 
with the electrodes in A, or with one in A and one in B. 
Gas is allowed to escape freely until one can be sure that all 
dissolved air is removed; the stop-cocks F’, F are now closed, 
and G opened, and the liquid in A and B allowed to sink until 
it just covers the electrodes. G is then closed, and F, F 
opened, when the gases may be introduced into the eudiometer 
in the ordinary way. The whole apparatus is attached to a 
mahogany slab, H, which fits into the box K—shown cut 
through the middle in the drawing—either, when in use, as 
represented, or, when not in use, as a lid, with the apparatus 
within the box. The box thus answers the double purpose of 
a convenient stand and a safe packing-case. 
