It was such a result that the patents of Clay and Lieb aimed to accomplish. In order to demonstrate the practicability of the system, the Electro-Pneumatic Transit Company had constructed in the basement of the Mills Building, on Broad Street, New York, a short line of small brass tubing, about two or three inches in diameter, with one branch, thus connecting three stations together. The tube was very short, probably not more than two hundred feet in length. The air-pressure required was very slight, probably not more than an ounce or two, being supplied by a small blower run by an electric motor. At the junction of the branch and the main tube was located a switch that could be moved across the main tube and so deflect the approaching carrier into the branch. This switch was moved by an electro-magnet, or solenoid, that could be excited by pressing a button at the station from which the carrier was sent. When the carrier passed into the branch tube it set the switch back into its normal position, so that a second carrier, following the first, would pass along the main tube, unless the switch was again moved by pressing the button at the sending station. This tube in the Mills Building worked well, but it was of a size only suited to the transmission of cash in a store or other similar service. It could not be said, because this tube worked well, that a larger and longer tube with numerous branches would work equally well. In fact, there are several reasons why such a tube would not operate satisfactorily. The method of operating the switches was impracticable. Suppose the branch tube had been located two miles away from the sending station and that it would take a carrier four minutes to travel from the sending station to the junction of the branch tube. Again, suppose that we have just despatched a carrier destined for a station on the main line beyond the junction, and that we wish to despatch the second carrier to be switched off into the branch tube, we must wait at least four minutes, until the first carrier has passed the junction, before we can press the button and set the switch for the second carrier which may be on its way. How are we to know when the first carrier has passed the junction, and when the second will arrive there, in order that we may throw the switch at the proper time? Must we hold our watch and time each carrier? It is plain that this is not practical. I take this as an illustration of the impracticability of the Clay-Lieb System as constructed in the Mills Building when extended to practical dimensions. I will not describe the mechanism and details of the system, which are ingenious, but will say in passing that the automatic sluice-gates, which work very well in a three-inch tube with carriers weighing an ounce or two and air-pressures of only a few ounces per square inch, would be useless and could not be made to operate in a six-inch tube with carriers weighing from eight to