We used platinum, and alloys of platinum and iridium, abandoned them as Edison did more than thirty years later, and then tried a multitude of forms of carbon, including that which constitutes the last "discovery" of Mr. Edison, viz., burnt cane. Starr tried this on theoretical grounds, because cane being coated with silica, he predicted that by charring it we should obtain a more compact stick or thread, as the fusion of the silica would hold the carbon particles together. He finally abandoned this and all the rest in favor of the hard deposit of carbon which lines the inside of gas-retorts, some specimens of which we found to be so hard that we required a lapidary's wheel to cut them into the thin sticks. Our final wick was a piece of this of square section, and about 1/8 of an inch across each way. It was mounted between two forceps--one holding each end, and thus leaving a clear half-inch between. The forceps were soldered to platinum wires, one of which passed upward through the top of the barometer tube, expanded into a lamp glass at its upper part. This wire was sealed to the glass as it passed through. The lower wire passed down the middle of the tube. The tube was filled with mercury and inverted over a cup of mercury. Being 30 inches long up to the bottom of the expanded portion, or lamp globe, the mercury fell below this and left a Torricellian vacuum there. One pole of the battery, or dynamo-machine, was connected with the mercury in the cup, and the other with the upper wire. The stick of carbon glowed brilliantly, and with perfect steadiness. I subsequently exhibited this apparatus in the Town-hall of Birmingham, and many times at the Midland Institute. The only scientific difficulty connected with this arrangement was that due to a slight volatilization of the carbon, and its deposition as a brown film upon the lamp glass; but this difficulty is not insuperable.--_Knowledge_. * * * * * ACTION OF MAGNETS UPON THE VOLTAIC ARC. The action of magnets upon the voltaic arc has been known for a long time past. Davy even succeeded in influencing the latter powerfully enough in this way to divide it, and since his time Messrs. Grove and Quet have studied the effect under different conditions. In 1859, I myself undertook numerous researches on this subject, and experimented on the induction spark of the Ruhmkorff coil, the results of these researches having been published in the last two editions of my notes on the Ruhmkorff apparatus. [Illustration: FIG. 1]