846 NOTICES OF THE MEETINGS [Jan. 20, 
remarkable illustrations of some fundamental principles of Electricity, 
and strong confirmation of the truthfulness of the view which I 
put forth sixteen years ago, respecting the mutually dependent nature 
of induction, conduction, and insulation (Experimental Researches, 
1318, &c.). Iam deeply indebted to the Company; to the Gutta 
Percha works, and to Mr. Latimer Clarke, for the facts; andalso for 
the opportunity both of seeing and shewing them well. 
Copper wire is perfectly covered with gutta percha at the Com- 
pany’s works, the metal and the covering being in every part 
regular and concentric. The covered wire is usually made into 
half mile lengths, the necessary junctions being effected by twisting 
or binding, and ultimately, soldering ; after which the place is covered 
with fine gutta percha, in such a manner as to make the coating as 
perfect there as elsewhere: the perfection of the whole operation 
is finally tried in the following striking manner, by Mr. Statham, 
the manager of the works. The half mile coils are suspended from 
the sides of barges floating in a canal, so that the coils are 
immersed in the water whilst the two ends of each coil rise into 
the air: as many as 200 coils are thus immersed at once, and when 
their ends are connected in series, one great length of 100 miles of 
submerged wire is produced, the two extremities of which can be 
brought into a room for experiment. An insulated voltaic battery 
of many pairs of zinc and copper, with dilute sulphuric acid, has one 
end connected with the earth and the other, through a galvanometer, 
with either end of the submerged wire. Neglecting the first effect, 
but continuing the contact, it is evident that the battery current 
can take advantage of the whole accumulated conduction or de- 
fective insulation in the 100 miles of gutta percha on the wire, and 
that whatever portion of electricity passes through to the water will 
be shewn by the galvanometer. Now the battery is made one of 
intensity, in order to raise the character of the proof, and the gal- 
vanometer employed is of considerable delicacy ; yet so high is the 
insulation that the deflection is not more than 5°. As another 
test of the perfect state of the wire, when the two ends of the battery 
are connected with the two ends of the wire, there is a powerful 
current of electricity shewn by a much coarser instrument; but 
when any one junction in the course of the 100 miles is separated, 
the current is stopped, and the leak or deficiency of insulation ren- 
dered as small as before. The perfection and condition of the 
wire may be judged of by these facts. 
The 100 miles, by means of which I saw the phenomena, were 
thus good as to insulation. The copper wire was =’; of an inch in 
diameter :—- the covered wire was 54; ; some was a little less, being 
<; in diameter : — the gutta percha on the metal may therefore be 
considered as 0.1 of an inch in thickness. 100 miles of like 
covered wire in coils were heaped up on the floor of a dry ware- 
house and connected in one series, for comparison with that under 
water. 
