354 NOTICES OF THE MEETINGS (Jan. 20, 
that as long as battery contact was continued, and then gradually 
diminished to nothing. Thus the record o shewed that the wave of 
power took time in the water wire to reach the further extremity ; by 
its first faintness, it shewed that power was consumed in the exertion 
of lateral static induction along the wire; by the attainment of a 
maximum and the after equality, it shewed when this induction had 
become proportionate to the intensity of the battery current; by its 
beginning to diminish, it shewed when the battery current was cut off ; 
and its prolongation and gradual diminution shewed the time of the 
outfiow of the static electricity laid up in the wire, and the consequent 
regular falling of the induction which had been as regularly raised. 
With the pens m and o the conversion of an intermitting into a 
continuous current could be beautifully shewn ; the earth wire by the 
static induction which it permitted, acting in a manner analogous to 
the fly wheel of a steam engine, or the air spring of a pump. Thus 
when the contact key was regularly but rapidly depressed and raised, 
the pen m made a series of short lines separated by intervals of equal 
length. After four or more of these had passed, then pen 0, belong- 
ing to the subterraneous wire, began to make its mark, weak at first, 
then rising to a maximum, but always continuous. If the action of 
the contact key was less rapid, then alternate thickening, and attenua- 
tions appeared in the o record; and if the introductions of the 
electric current at the one end of the earth wire were at still longer 
intervals, the records of action at the other end became entirely 
separated from each other. All shewing most beautifully, how the 
individual current or wave, once introduced into the wire, and 
never ceasing to go onward in its course, could be affected in its 
intensity, its time, and other circumstances, by its partial occupation 
in static induction. 
By other arrangements of the pens z and o, the near end of the 
subterraneous wire could be connected with the earth immediately 
after separation from the battery; and then the back flow of the 
electricity, and the time and manner thereof, were beautifully 
recorded ; but I must refrain from detailing results which have 
already been described in principle. 
Many variations of these experiments have been made and may 
be devised. Thus the ends of the insulated battery have been 
attached to the ends of the long subterraneous wire, and then 
the two halves of the wire have given back opposite return cur- 
rents when connected with the earth. In such a case the wire is 
positive and negative at the two extremities, being permanently 
sustained by its length and the battery, in the same condition 
which is given to the short wire for a moment by the Leyden 
discharge (p. 351); or, for an extreme but like case, to a filament of 
shell lac having its extremities charged positive and negative. 
Colomb pointed out the difference of long and short as to the 
insulating or conducting power of such filaments, and like difference 
occurs with long and short metal wires. 
