conducting material just referred to assisted the formation of the arc at that point, and the resulting intense heat maintained the plaster in a moderately conducting state until the whole carbon was consumed.  Here, then, was literally an electric “candle,” which could be operated without the costly and unsteady lamps, and fortunately its birthplace was Paris—­then the center of philosophical research; from that period the future of electric lighting was assured.

When we reflect that owing to the greater disruptive energy of the positive terminal, the carbon so connected to an ordinary dynamo machine is consumed very much faster than the negative—­sometimes in the ratio of 3 to 1—­it will be clear that some other means of consuming the Jablochkoff candle had to be used, since the arc would cease to exist in a very short time by reason of the unequal consumption of the carbons, and the subsequent increase of the intervening space beyond the limit of the current tension.

This difficulty M. Gramme overcame with characteristic ingenuity by adding to the ordinary system a “distributer” capable of delivering plus and minus currents alternately, thus equalizing the consumption, besides being able to supply a large number of candles on the multiple circuit system, each circuit supporting four or five lamps.  Thus it will be seen that a result was attained which at least gave such men as Siemens, Gramme, and their peers, if such there be, confidence in the future and a courage which quickly placed the new science safely beyond the limits of the laboratory.  I will not occupy your time by stating the apparent reasons why the Jablochkoff candle has not fully sustained its brilliant promise—­it will, perhaps, be sufficient to state that it is now superseded practically, though it must always occupy an honorable place in scientific annals.

Let us now for a few moments consider what the electric light really accomplished at about this period, I mean from an economical standpoint.  It appears from some data furnished by an engineer commissioned by the French Government that the machines were then capable of maintaining a light equal to from 220 to 450 candles, measured by comparison with the Carcel burner, per horse power absorbed—­a very good showing considering the youth of the discovery, but presenting rather a gloomy aspect when we consider that according to Joule’s mechanical equivalent of heat, which is 772 foot pounds, or the power required to raise one pound of water one degree—­and for lack of anything better, we are obliged to accept that at this moment—­the whole force contained in one pound of coal would maintain a light equal to 13,000 candles for one hour!  That is the ultimate force, and what we are now able to accomplish is but a small fraction of this amount.

Unfortunately we are but common mortals, and cannot, like Mr. Keely, lightly throw off the trammels of natural law; we must, therefore, endeavor to close this gap by patient study and experiment.