This machine has been studied with a view of rendering the lamps independent; and there may be produced with it, for example, a voltaic arc of an intensity of from 250 to 600 carcels for the lighting of a courtyard, or it may be used for producing arcs of less intensity for shops, or for supplying incandescent lamps.  As each of the circuits is independent, it becomes easy to light or extinguish any one of the lamps at will.  Since the conductors are formed of ordinary simple wires, the cost attending the installation of 12 or 24 lamps amounts to just about the same as it would in the case of a single cable.

[Illustration:  Gerard’s 250 H.P.  Direct connection alternating current steam dynamo-electric machine.]

One of the annexed cuts represents a Corliss steam engine connected directly with an alternating current machine of the system under consideration.  According to the inventor, this machine is capable of supplying 1,000 lamps of a special kind, called “slide lamps,” and a larger number of incandescent ones.—­Revue Industrielle.

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AUTOMATIC FAST SPEED TELEGRAPHY.

By Theo.  F. Taylor.

Since 1838 much has been done toward increasing the carrying capacity of a single wire.  In response to your invitation I will relate my experience upon the Postal’s large coppered wire, in an effort to transmit 800 words per minute over a 1,000 mile circuit, and add my mite to the vast sum of knowledge already possessed by electricians.

As an introduction, I shall mention a few historical facts, but do not propose to write in this article even a short account of the different automatic systems, and I must assume that my readers are familiar with modern automatic machines and appliances.

In 1870, upon the completion of the Automatic Company’s 7 ohm wire between New York and Washington, it happened that Prof.  Moses G. Farmer was in the Washington office when the first message was about to be sent, and upon being requested, he turned the “crank” and transmitted the message to New York, at the rate of 217 words per minute.

Upon his return to New York he co-operated with Mr. Prescott in experiments on W.U. wires, their object being to determine what could be done on iron wires with the Bain system.  A good No. 8 wire running from New York to Boston was selected, reinsulated, well trimmed, and put in first-class electrical condition, previous to the test.  The “Little” chemical paper was used.

The maximum speed attained on this wire was 65 words per minute.

About the same time George H. Grace used an electro magnet on the automatic line with such good effect that the speed on the New York-Washington circuit was increased to 450 words per minute.

Then a platina stylus or pen was substituted for the iron pen in connection with iodide paper, and the speed increased to 900 words per minute.