900 
anstalt. The switch S for closing and opening the current served 
for measuring off the time. Fig. 6 represents the complete arrangement *) 
for measuring off and registering the time. The clock U with 
second pendulum, provided with a Honwé registering arrangement H, 
closes, respectively opens in passing 
its equilibrium position a current 
which operates a relais Q. This closes, 
respectively opens a current, which 
makes the bell £ give a stroke every 
two seconds; this is registered by 
the telegraphic apparatus 7’ the 
Morse-key J/ being in its position 
of rest. If, after contact has been 
made at 7 by a plug, M is pressed 
down at a moment that no current 
goes through (to be recognized from 
the position of the tongue of the bell), 
at the next closing of the current 
by the relais the beam j; of the 
contact-key S; (see Fig. 7) will be 
released, the platinum wire p,, will 
fall into the mercury, and the heating 
current through the constantin wire 
wil be closed *). The switching out 
Fig. 7, is operated in the same way by S, 
the contact plug having been transferred from 7 to wv. As a control 
the moments of switching in and out are registered by 7’ (Fig. 6) 
through the corresponding dash on the paper strip being absent. 
An accuracy of '/,, of a second is certainly attained with this 
arrangement. 
Cy 
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The temperature measurement. The scale of the gold resistance 
thermometer is dealt with in § 3. In Fig. 6 the THomson bridge 
') This arrangement was already used in the determination of the heat of 
vaporisation of hydrogen, cf. Comm. N°. 137e. 
2) The distances of the points of pi, and pu, (fig. 7) above, and below the 
respective mercury surfaces (covered with paraffin oil partly for suppressing the 
opening spark) are small and are made equal to each other by adjusting the 
mereury cups, whereas the velocity of fall of the two beams ji and ju was also 
made as equal as possible. The two other cups (see pit and u2) may serve to use 
the apparatus as a switch-over key (e.g. if the same wire has to be used as a 
heating and as athermometer wire, cf. §3 at the end); in the present experiments 
they were not filled with mercury. 
