TELEGRAPHIC APPARATUS. 
225 
by turning the screw that raises or lowers the fixed contact, 
and when cnee this has been adjusted it is left undisturbed. 
When the ink is not sufficiently electrified although the mill 
is turning properly and appears to be generating a proper 
supply of electricity, the rod p must first of all be brought near 
the plate 0 . The ordinary distance is from 2 to 3| inches. A 
piece of paper is sometimes placed between the rod and the 
plate to facilitate the electrification of the ink. This depends 
however upon the hygrometric state of the atmosphere. We 
must make sure that the apparatus supporting the siphon is 
perfectly insulated and to make it so, all dust must be removed 
by a badger-hair brush or by a feather from the silk fibre guides. 
The piece of ebonite supporting the whole is always covered by 
a layer of paraffin to keep the insulation perfect. The solid 
piece of paraffin that supports the rod p and insulates it from 
the insulated inducer, also requires attention ; for dust may be 
deposited upon it so that the electricity escapes over its surface. 
When the mill turns easily but without giving off electricity, 
it is necessary first to take off the cover and carefully remove 
the inducer covered with paraffin to see if its insulation is per¬ 
fect ; then, to see if the four gold contacts properly touch the 
pieces of copper. 
If the mill gives off too much electricity, the siphon, instead 
of giving a straight line, will vibrate laterally, and the signals 
will be distorted. The excess of electricity is removed by 
carrying some off by means of a metallic point placed in contact 
with the outside of the mill, and directed towards the rod p. 
The connections of the siphon recorder are usually made as 
shown in fig. 161. The current from the line, after having 
passed through the signal coil, and a properly adjusted shunt, s, 
returns to earth through a condenser of about 2 or 3 microfarads 
for every hundred miles of cable. A commutator of a novel 
form (fig. 159) invented by Mr. B. Smith, takes the line current 
to earth when the handle is turned to the right, and when 
turned to the left, the current is transmitted. In the inter¬ 
mediate position, shown in the figure, the line wire is directly 
put to earth to be discharged. In some stations the condenser 
is placed between the line and the apparatus, and not between 
the apparatus and the earth as in our design. In these cases 
the transmitted signals, as well as the received signals, pass 
Q 
