the earth or the sea.  It is also said that during an east-going storm it was found impossible to work the telegraph lines between New York and Buffalo, but on taking off the batteries at both ends and looping the ends of the wire in the air, that a constant current of electricity passed from Buffalo to New York, and the line was kept in constant use in that direction without any battery connection until the storm abated.  Now, how far or to what advantage we may be able to utilize this differential tension of electricity in the earth and the air, we cannot now say; but I think that we may justly look for valuable developments in this direction.

If, as I verily believe, a process will soon be discovered by which dynamic caloric can be produced by the oxidation of petroleum with non-luminous combustion in an insulated chamber, as we now oxidize zinc, electricity will then be obtained from so small a weight, and at such a low cost, as to insure aerial navigation beyond a doubt.  Not with balloons and their cumbrous inflations, but with machines capable of carrying the load, and traveling by displacement of the air at high velocities.  Therefore we may expect that aerial navigation will be developed in the near future to be one of the greatest enterprises of the world.

And lastly, will it pay to use luminous combustion as a first power for generating dynamic caloric for use as a second power, as is now practiced?

At the University of Pennsylvania, in Philadelphia, gas is consumed in an Otto gas engine, which drives a Gramme generator; and the lecture room is lighted with electricity, and I am informed that the light is both better and cheaper than when they used the gas in the ordinary gas burners.  Hence we may expect to see gas consumed to advantage for producing electric lights.

Considering the difficulties of transmitting steam power to a considerable distance, and the comparative great cost of running small engines, it is more than likely that electricity as at present generated will be found to be economical for driving small motors.

Having thus endeavored to explain what electricity is, and the laws which govern the occlusion of static caloric, and the development of dynamic caloric (electricity), in conclusion I call the attention of the inventors of the age to the great need of a process for oxidizing coal or oil at a low degree, within an insulated vessel.  With such an invention electricity would be obtained at such a low cost that it would be used exclusively to light and heat our houses, to smelt, refine, and manipulate our metals, to propel our cars, wagons, carriages, and ships, cook our food, and drive all machinery requiring motive power.

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ELECTRIC LIGHT APPARATUS FOR PHOTOGRAPHIC PURPOSES.

By A.J.  JARMAN.