_An Interesting Experiment of Supporting a Large Bar of Iron within the Helix. Discovered by Mr. Vail, January, 1844._ It has been shown, many years since, that a magnetic needle would be drawn into and suspended within a helix, conveying a galvanic current, and that in the case of using large bar magnets, the coils or helices might be made to move over them, as in De La Rives’s rings; but in no instance, I believe, has it been recorded, or observed, that a bar of iron weighing a pound or more, could be drawn up into the helix and there sustained in the air, as it were, without support. If the helix, as shown in figure 30, be connected with from 6 to 12 pairs of Grove’s battery, the bar may be drawn up into its centre and there sustained in a vertical position by the action of the helix, forming an exceedingly interesting and paradoxical experiment. [Illustration: FIG 30.] [From the National Intelligencer.] APPLICATION OF THE ELECTRO MAGNETIC TELEGRAPH TO THE DETERMINATION OF LONGITUDE. Among the wonderful developements of the new telegraph, one has just came to light which will be regarded in the world of science as deeply interesting. Prof. Morse suggested to the distinguished Arago, in 1839, that the electro magnetic telegraph would be the means of determining the difference of longitude between places with an accuracy hitherto unattainable. By the following letter from Capt. Charles Wilkes to Prof. Morse, it will be believed that the first experiment of the kind of which we have any knowledge, has resulted in the fulfilment of the Professor’s prediction. WASHINGTON, _June 13, 1844_. MY DEAR SIR—The interesting experiments for obtaining the difference of longitude through your magnetic telegraph were finished yesterday and have proved very satisfactory. They resulted in placing the Battle Monument square, Baltimore, 1 _m_, .34 sec. .868 east, of the capitol. The time of the two places was carefully obtained by transit observations. The comparisons were made through chronometers and without any difficulty. They were had in three days, and their accuracy proved in the intervals marked and recorded at both places. I have adopted the results of the last day’s observations and comparisons, from the elapsed time having been less. The difference of the former results, found in the American Almanac, is .732 of a second. After these experiments, I am well satisfied that your telegraph offers the means for determining meridian distances more accurately than was before within the power of instruments and observers.