Pole of magnet pointing toward the north. N The opposite pole. S Force of a pole, quantity of magnetism. _m_ Distance of the poles of a magnet. _l_ Magnetic moment. M = _m.l_ Intensity of magnetization. J Intensity of the horizontal component of terrestrial magnetism. H C.--ELECTRIC MEASUREMENTS. Galvanometer and its resistance. G Resistance of the shunt of a galvanometer. _s_ Battery and its internal resistance. B For dynamo machines, the following designations are proposed: 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.