In the absence of experience, the expense necessary to construct and to maintain a system of electro magnetic telegraphs, was thought to be so great as to present a formidable, if not an insurmountable obstacle to its adoption. But the experiment already made for 40 miles, has shown that the electro magnetic telegraph is far from being expensive, either in its first construction, or after maintenance, especially when its vast superiority over the old system is taken into consideration. To make this more clear, I give an abstract both of the expenses and capacities of the ordinary visual telegraphs in some of the European countries. In England, the semaphore telegraph, established between London and Portsmouth, a distance of 72 miles, is maintained by the British government at an average expense of _£_3,405, or $15,118 per annum. From a return [vol. 30, 1843, accounts and papers of House of Commons] of the number of days during which the telegraph was _not available_, on account of the weather, during a period of three years, it appears that there were, in that time, 323 days in which it was useless, or nearly _one year out of three_! But by a return made to the admiralty of the number of hours in the day appointed for working the telegraph, it appears that the hours appointed for the year are—from 1st October to 28th February, from 10 o’clock, a. m., to 3 p. m.; 5 hours. From 1st March to 30th September, from 10 a. m., to 5 p. m.; 7 hours. Average number of hours per day, in the most favourable weather, 6 hours! Deducting 1 year from the 3, for unavailable days, the average time per day for the 3 years would be but 4 hours. So that, for the use of their telegraph for 72 miles, and for only 4 hours in the day, the British government expend $15,118 per annum. The French system of telegraphs is more extensive and perfect than that of any other nation. It consists, at present, of five great lines, extending from the capital to the extreme cities of the kingdom, to wit: The Calais line, from Paris to Calais, 152 miles The Strasbourg line, from Paris to Strasbourg, 255 “ The Brest line, from Paris to Brest, 325 “ The Toulon line, from Paris to Toulon, 317 “ The Bayonne line, from Paris to Bayonne, 425 “ ————————— 1,474 miles. ============= Making a total of 1,474 miles of telegraphic intercourse. These telegraphs are maintained by the French government at an annual expense of over 1,000,000 of francs, or $202,000.