The machine itself. D
Positive terminal. +T
Negative terminal. -T
Magnet forming the field. FM
Current indicator (amperemeter). AM
Tension indicator (voltameter). MV
Electro-magnet. EM
Luminous intensity of a lamp, in candles. _c.p_.
Resistance of the armature. R_{a}
Resistance of the magnet forming the field. R_{m}
Resistance of the external circuit. R_{o}
Intensity in the armature. C_{a}
Intensity in the coils of the magnet. C_{m}
Intensity in the external circuit. C_{e}
Coefficient of self-induction. L_{s}
Coefficient of mutual induction. L_{m}

A primary battery would be represented as in Fig. 1, and a battery of
accumulators as in Fig. 2.

[Illustration: FIG. 1.]

[Illustration: FIG. 2.]

In order to designate incandescent lamps, circles would be used, and
stars for arc lamps. A system of incandescent lamps arranged in multiple
arc would be represented as in Fig. 3.

[Illustration: FIG. 3.]

Fig. 4 and the formula

R = B + Gs/(G + s) + r

would serve for the total resistance, R, of an electric circuit, upon
giving the letters the significations adopted.

[Illustration: FIG. 4.]

Such is, in brief, the present state of the question. The scientific
bodies that have taken hold of it have not as yet furnished a fully
co-ordinated work on the subject. Let us hope, however, that we shall not
have to wait long. The question is of as much interest to scientific men
as to practical ones.

A collection of identical symbols would have the advantage of permitting
us to abridge explanations in regard to the signification of terms used
in mathematical formulas. A simple examination of a formula would suffice
to teach us its contents without the aid of tiresome explanatory matter.

But in order that the language shall be precise, it will be necessary for
the words always to represent precise ideas that are universally
accepted, and for their sense not to depend upon the manner of
understanding the idea according to their arrangement in the phrase.

Nothing can be more desirable than that the societies of electricians of
all countries shall continue the study of t