ELECTROLYTIC REGISTERING METER.

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compared with the resistances in series with them. It will beunderstood that after each measurement or registration of a givenvariation of resistance in one or both conductors, the direction ofthe current should be changed or the instrument reversed, so thatthe deposit will be taken from the conductor which has gainedand added to that which has lost. This principle is capable ofmany modifications. For instance, since there is a section of thecircuit—to wit, the conductor o or o'—that varies in resistance inproportion to the current strength, such variation maybe utilized,as is done in many analogous cases, to effect the operation ofvarious automatic devices, such as registers. It is better, how-ever, for the sake of simplicity to compute the energy by meas-urements of resistance.

The chief advantages of this arrangement are, first, that it ispossible to read off directly the amount of the energy expendedby means of a properly constructed olim-meter and without re-sorting to weighing the deposit; secondly it is not necessary toemploy shunts, for the wdiole of the current to be measured maybe passed through the instrument; third, the accuracy of the in-strument and correctness of the indications are but slightly af-fected by changes in temperature. It is also said that such metershave the merit of superior economy and compactness, as well asof cheapness in construction. Electrolytic meters seem to needevery auxiliary advantage to make them permanently popular andsuccessful, no matter how much ingenuity maybe shown in theirdesign.