=Practical Beginning of the Art. The London Pneumatic Telegraph.=—London has the honor of being the first city to have a practical system of pneumatic telegraphy. The first tubes were installed by the Electric and International Telegraph Company, the work being planned and carried out by their engineer, Mr. Josiah Latimer Clark, in 1853 and 1854. The first tube to be laid was one and one-half inches in diameter, and extended from the central station, Founder’s Court, Lothbury, to the Stock Exchange, Throgmorton Street, a distance of two hundred and twenty yards. The tube was operated intermittently by connecting it to a vacuum chamber at the central station. Carriers were sent only in one direction. A steam-pump was used to maintain the vacuum. Much experience was gained from the use of this first tube. In 1858 some improvements were made by Mr. C. F. Varley, and I can best describe them by quoting from the discussion of Mr. Carl Siemens’s paper on “Pneumatic Despatch Tubes: The Circuit System” before the Institution of Civil Engineers, as recorded in the minutes of that society. “Later, about the year 1858, when a pipe two and one-fourth inches internal diameter was extended from Telegraph Street to Mincing Lane, thirteen hundred and forty yards in length, the traffic was so considerable that it was found desirable to have the power of sending messages in both directions. To effect that a smaller pipe, one and one-half inches in internal diameter, was laid between Telegraph Street and Mincing Lane, with a view to carrying the vacuum to the latter station, so as to take messages in the opposite direction. This smaller pipe was found to so wiredraw the current that the pipe would not work, the leakage past the carrier being too considerable; and accordingly a large chamber was built in the basement floor or kitchen at the corner of Mincing Lane and Leadenhall Street to collect power or vacuum for bringing the messages from Telegraph Street to Mincing Lane. This chamber was constructed of timber, fourteen feet by twelve feet broad and ten feet high, and was covered with lead. It was not strong enough to withstand the pressure; for one day, a carrier having stuck half-way, and when there was a higher vacuum than usual,—viz., twenty-three inches of mercury,—it collapsed with a loud report. At the time the landlord of the house happened to be dining in the next room, and he suddenly found himself, his table, dinner, and the door, which was wrenched off its hinges, precipitated into the room amongst the _débris_ of the chamber. The windows were forced inwards, and those on the opposite side of Mincing Lane and Leadenhall Street were drawn outwards. The damage was considerable. This accident put an end, for a time, to the attempt to send telegraph messages by means of a vacuum conveyed through this smaller pipe. About that time he (Mr. Varley) became the engineer-in-chief of the Electric Telegraph Company, and