215 
will be mounted on the axis of a vaN Harrrverp’s clinostat. The 
electric connections will be secured, in that case, by sliding-contacts 
on the clinostat-axis. 
As Bovie (le) has already mentioned, it is a great advantage 
that the test-plant may be as far as desirable from the recording 
apparatus. In our case, the latter has been placed in quite another 
part vof the building. ah 
The relais. As remarked above, a weak current is closed by the 
plant. In order to eliminate sparking at the interruption of the 
current, a condenser or a resistance (parallel to the contact). could 
be inserted into the curcuit. In the latter case, the resistance ought 
to ‘be less: than the atmospheric resistance, but large enough to, 
prevent the relais to react. [t can, however, be eliminated more 
safely by using a current of very low voltage, led through a 
fit relais. This relais has been found in the form of a galvanometer,’ 
with two coils of 4000. windings each. On the mirror of this gal- 
vanometer an iron electrode (81) (see fig. 3) is fixed, on which two; 
platinum tips have been soldered. When the mirror (with the elec- 
trode) turns, these platinum tips are moved into two small cups, 
filled with mercury (82), whereby a second circuit is closed. 
i This galvanometer, 
in transformed into a relais, 
has the following ad- 
vantages : Lind 
ae | pana ME First. It has an extra- 
Sr \ ordinary high sensiti- 
NA) (9  T@ veness. 
ey B Ad 
AE YS it Second. As there is 
pe no iron pith, in contrast 
with other kinds of 
Le Smi 
8 | fe | i relais, the self of the 
| | bs LORETO | current is so small, that: 
| at the opening no spark 
will occur. 
Third. The turning of the mirror takes a rather long time ; the relais: 
having a great inertia. Short current-pulses, as will result from 
vibrations, do not possess enough turning-power, to make the electrode 
(31) reach the mercury (82). In order to obtain this result, the 
circuit is to be closed at least for '/, second. . | út 
In this simple method the influence of vibrations is efficiently: 
eliminated. » | | i dt Linh 
Fig, 3. The galvanometer, transformed into a relais. 
