got permission from the directors to introduce a new system,—viz., compressed air,—though many persons contended that it would be impossible to blow messages through a pipe, because all attempts to blow air through long pipes had utterly failed; while others said that, if messages were sent, they would go much slower than with the vacuum.... In his (Mr. Varley’s) apparatus, for he was the first to introduce compressed air, the reverse was found to be the case, and for this reason: the tube did not consume power until a message was about to be forwarded; and in a tube thirteen hundred yards in length, and two and one-fourth inches in diameter, fifteen seconds elapsed before the vacuum was felt at the distant end after communication had been established with the exhausted chamber at the engine end of the tube, consequently the carrier did not start until after fifteen seconds had elapsed. When a message was sent by compressed air, it was sent from the end at which the power was applied, and the carrier started at once, thus gaining a start of fifteen seconds; now, inasmuch as the air in the tube had to be compressed, it started at a very high velocity, and when it reached the other end the compressed air in expanding gave it a higher velocity. The result was, in thirteen hundred and forty yards, from Telegraph Street to Mincing Lane, the carriers were drawn by vacuum, on an average, in from sixty to seventy seconds, and were propelled by compressed air in about fifty or fifty-five seconds, the difference of pressure in each case being nearly equal.” The first one and one-half inch tubes laid under the direction of Mr. Clark were of iron with screwed joints. They gave much trouble from roughness upon the interior, which wore the carriers very rapidly, and from water that was drawn in through leaky joints. When the extensions were made in 1858 and afterwards, two and one-fourth inch lead tubes were used with plumber’s joints made over a heated mandrel, which made the joints very smooth upon the interior. The carriers were of gutta percha in the form of a cylinder closed at one end and fitted with a cap at the other. The outside was covered with felt or drugget. When a carrier was to be despatched, a signal was sent to an attendant at the pump end of the tube, who closed that end and connected the tube to an exhausted chamber by opening a valve. As soon as the carrier arrived, he closed the valve and opened the tube, which allowed the carrier to drop out. Mr. Varley improved the method of operating the valves by making the air pressure do the work by means of cylinders and pistons when the attendant pressed a button. He also improved the carriers by doing away with the cap and using in its place an elastic band to hold the messages in place.