Method of Manufacturing Tubes.

—The process of boring was novel in some respects, and might be termed reaming rather than boring. Figs. 4 and 5 show the interior of the shop and the twelve machines. Fig. 6 is a drawing of one of the machines. A long flexible bar rotated the cutter-head, which was pulled through the tube, in distinction from being pushed. In order to give the feeding motion, a screw was attached to the cutter-head and extended through the tube in advance of it. The feed-screw was drawn forward by a nut attached to a hand-wheel located at the opposite end of the tube from which the boring began. Since it was not necessary that the tubes should be perfectly straight, a method of this kind was permissible, in which the cutters could be allowed to follow the cored axis of the tube. Air from a Sturtevant blower was forced through the tubes during the process of boring, for the double purpose of clearing the chips from the cutters and keeping them cool. After the tubes were reamed, each piece had to be placed in a lathe, have a counter-bore turned in the bottom of the bell, and have the other end squared off and turned for a short distance on the outside to fit the counter-bore of the next section.

Laying and Opening the Tubes for Traffic.

—The first tubes were laid about the middle of November, but December 1 came before the work was completed and special permission had to be obtained from the city to carry on the work after that date. All work was suspended during the holidays in order not to interfere with the holiday trade of the stores on Chestnut Street. Severe frosts prevailed at that season, so that when the work was begun again, after the holidays, bonfires had to be built in the streets to thaw out the ground in order to take up the paving-stones and dig the trench for the tubes. Several times the trench was filled with snow by unusually heavy storms. Notwithstanding all these delays and annoyances, the work was pushed forward, when a less determined company would have given it up, and was finally completed. A formal opening took place on February 17, 1893, when Hon. John Wanamaker, then Postmaster-General, sent through the tube the first carrier, containing a Bible wrapped in the American flag.

It was certainly a credit to the Pneumatic Transit Company and its managers that they were able to complete this first line of tubes so quickly and successfully under such trying circumstances. The tubes have been in successful operation from the opening until the present time, a period of nearly four years, and the repairs that have been made during that time have not required its stoppage for more than a few hours.

In the summer of 1895 the sub-post-office was removed from Chestnut Street to the basement of the Bourse (see Fig. 7). This required the abandonment of a few feet of tube on Chestnut Street and the laying of a slightly greater amount on Fourth Street, thus increasing the total length of the tubes a little. Wrought-iron tube, coated with some alloy, probably composed largely of tin or zinc, was used for this extension. The wrought-iron tube is not as good as the bored cast iron.

Fig. 7.
BOURSE BUILDING, PHILADELPHIA.

Fig. 8.
PNEUMATIC TUBES SUSPENDED IN THE BASEMENT OF THE MAIN POST-OFFICE.