_The First Land Telegraphs._--The first practical telegraph-line in the world--namely, that on the Great Western Railway from Paddington to West Drayton, shortly afterward extended to Slough--was within the year of Queen Victoria's accession to the throne, and in the same year as the first trunk line of railway and the first ocean steamer.[1] Improvements and novelties in telegraphic instruments were rapidly made by inventors from all the civilized nations--e. g., Morse, Vail, and Henry in America; Breguet in France; Steinheil and Siemens & Halske in Germany; and Schilling in Russia; besides Alexander Bain, Bright, and Hughes in England. Commercial interests were soon formed to work the new invention, and in England the Electric and International Telegraph Company, the British and Irish Magnetic Telegraph Company, and other large concerns were the means of establishing telegraphic communication throughout the kingdom--only to be absorbed by Government later on. Our theme does not include--even in the course of introduction--a study of the development of land telegraphy. The apparatus and methods employed are, to a great extent, entirely different; indeed, the only point in common between the cardinal principles and submarine telegraphy is that electricity, as generated by a voltaic battery, is the common agent, and consequently the metal conducting-wire is employed in both.[2] But in subaqueous (as well as in subterranean) telegraphy the poles and porcelain insulators require to be substituted by an insulating covering round the entire conductor; and the point of contact in practise between land and marine telegraphy is really, therefore, in the matter of insulation for subterranean or subaqueous wires. _First Submarine Cables._--A Spaniard named Salva appears to have suggested the feasibility of submarine telegraphy as far back as 1795, and in 1811 Sommering and Schilling conducted a series of experiments, more or less practical, when a soluble material--said to have been india-rubber--was first used for insulating the wire.