In a communication that he has addressed to us on the subject of these bells, Mr. Lippens adds a few details in regard to the mode of applying the ground pile to micro-telephone stations.
Being given any two stations, he puts into the ground at the first a copper plate, and at the second a zinc one, and connects the two by a line wire provided with two vibrating bells and two telephone apparatus. The earth current suffices to actuate the bells, but, in order to effect a call, the inventor is obliged to run them continuously and to interrupt them at the moment at which he wishes to communicate. The correspondent is then notified through the cessation of noise in the bells, and the two call-apparatus are thrown out of the circuit by the play of the commutator, and are replaced by the micro-telephone apparatus.
It is certainly impracticable to allow vibrating bells to ring continuously in this manner. The ground pile would, at the most, be only admissible in cases where the call, having to be made from only one of the stations, might be effected by a closing of the circuit.—La Lumiere Electrique.
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The advantage of lighting vessels by electricity was shown when the steamer Carolina, of the old Bay Line between Baltimore and Norfolk, ran into the British steamship Riversdale in a dense fog off Cedar Point, on Chesapeake Bay. The electric lights of the Carolina were extinguished only in the damaged part of the boat, and her officers think that if she had been lighted in any other way, a conflagration would have followed the collision.
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PHOTO PLATES—WET AND DRY.
Dr. Eder has recently published, in the Correspondenz, the first of a series of articles embodying the results of his more recent work on gelatino bromide; and we now reproduce the substance of the article in a somewhat abstracted form.
The “sensitiveness of a wet” plate continues to be used as a rough and ready standard of comparison; and, notwithstanding the fact that it is physically impossible to exactly compare the sensitiveness of a wet plate with that of a gelatino bromide film, it is convenient to refer to wet plates as some kind of a rough standard.
Experiments have shown that a gelatine plate which gives the number 10 on the Warnerke sensitometer, may be regarded as approximately corresponding to the average wet plate; and setting out from this point, the following table has been constructed:
Sensitometer Sensitiveness, expressed in terms number. of a “Wet Plate.”
10 1 11 1-1/3 12 1-3/4 13 2-1/3 14 3 15 4 16