4 
Associated cases of Current and Static Effects. 85 
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 ex- 
tremities 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. Passing by the first effect, and continuing the 
contact, it is evident that the battery current can take advantage 
of the whole accumulated conduction or defective insulation in 
the 100 miles of gutta percha on the wire, and that whatever 
portion of electricity passes through to the water will be shown 
by the galvanometer. Now the battery is made one of intensity, 
in order to raise the character of the proof, and the galvanometer 
h 
little less, being ,,nds 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 warehouse and connected in one series, for comparison 
with that under water. 
. Consider now an insulated battery of 360 pairs of plates (4 x3 
he hes) having one extremity to the earth; the water wire with 
th its insulated ends in the room, and a good earth discharge 
Wite ready for the requisite communication: when the free bat- 
tery end was placed in contact with the water wire and then re- 
moved, and afterwards a person touching the earth discharge 
touched also the wire, he received a powerful k. ‘The shock 
48 rather that of a voltaic than of a Leyden battery; it occu- 
Pied time, and by quick tapping touches could be divided into 
numerous small shocks; I obtained as many as forty sensible 
