776 
the high pressure tube, B the small rotating endpiece, containing the half-shadow 
nicol and slit, Z the large fixed endpiece, containing the analyser, G a screw with 
a wheel, by which with the steel wire H and the weight J the endpiece B 
may be rotated, PQ the spectrograph. 
In series with the coils are: 
The main switch Aj, two dial resistances Wy and Wyy indicating to 001 ohm 
coupled in parallel, a manganin resistance across which is shunted a resistance box 
Fig. 1. 
in series with a moving coil galvanometer (clock model) by HARTMANN and BRAUN, 
an auxiliary switch By in parallel with a sliding resistance, through which the 
current is switched before being broken so as to diminish the intensity of the spark. 
