Miscellaneous Intelligence. 445 
> least a of _— powders, however fine, will endanger 
teration in the form of the mirror, and destroy the sharpness of 
us aaiable of aig produced ~ it. The greatest care must be 
to keep the peatber eo and dr 
mp 
In the sai ah of this shoes mention is made of a remarkable 
ffect observed Ma 
ph wires, which are found to have a direction more or less approach- 
to that of the declination needle, in order to make with them, when 
are not in use for ordinary purposes, some observations "which 
enable us to “ett and to measure. the electric currents 
probably travetse them.” 
My object in addressing you:is to state, ‘hal in the aa part of ea 
was led to undertake extensive aloneraiiony on this subject, in ¢ons 
of the peculiar disturbances occasionally visible on the fate: 
h instruments of the Midland Railway (on which line the telegraph 
erected under my superintendence as the company’s engineer). 
disturbances were at first attributed to atmospheric electricity 
to jo explain th e éffects, it is necessary to State that the Midland 
aoele coosisis of four principal lines centering in Derby, 
. From m Darky northwards to Leeds. -* 
From Derby northeast to Lincoln, ° 
From Derby southwards to Rugby. 
From Derby southwest to Birmingham 
disturbances on these four telegraphs were observed to occur 
with rare exceptions ; and the direction of the current 
9 say, when the deflection was such as to indicate that the current 
owards Derby on the first two, it was from Derby on the last two ; 
when it changed in one, it changed in all. It was also observed 
that on the 19th of March 1847, there was - unusual degree of dis- 
a set of experimenis on the subject. 
ving obtained delicate galvanometers, I first ascertained that cur- 
rents are at all times perceptible in the telegraph wires to a ernie or 
