following experiment: Two immovable metallic plates
constitute the armatures of a charged condenser, and attract
each other with a force, F. If the plates are insulated, these
charges remain constant, as well as the force, F. If, on the
contrary, we connect the armatures of resistance, R, their
charges diminish and the force, F, becomes a function of the
time, _t_; the time, _t_, inversely becomes a function of P. We
find _t_ by the following formula:

t = [rho] x (lS / S[pi]es) x log hyp(F0/F)

F0 and F being the values of the force at the beginning and
at the end of the time, _t_. The above formula is independent of
the choice of units. If we wish _t_ to be expressed in seconds,
we must give [rho] the corresponding value ([rho] = 1.058 X
10^-16). If we take [rho] as a unit we make [rho] = 1, and we
find the absolute value of the time by the expression:

(lS) / (8[pi]es) log hyp(F0/F)

We remark that this expression of time contains only abstract
numbers, being independent of the choice of the units of length
and force. S and _e_ denote surface and the thickness of the
condenser; _s_ and _l_ the section and the length of a column of
mercury of the resistance, R. This form of apparatus enables us
practically to measure the notable values of _t_ only if the
value of the resistance, R, is enormous, the arrangement
described in the text has not the same inconvenience.]

A battery of an arbitrary electromotive force, E, actuates at the same
time the two antagonistic circuits of a differential galvanometer. In
the first circuit, which has a resistance, R, the battery sends a
continuous current of the intensity, I; in the second circuit the
battery sends a discontinuous series of discharges, obtained by
charging periodically by means of the battery a condenser of the
capacity, C, which is then discharged through this second circuit. The
needle of the galvanometer remains in equilibrium if the two currents
yield equal quantities of electricity during one and the same time,
[tau].

Let us suppose this condition of equilibrium realized and the needle
remaining motionless at zero; it is easy to write the conditions of
equilibrium. During the time, [tau], the continuous current yields a
E
quantity of electricity = -- [tau]; on the other hand, each charge of
R
the condens