A special air-compressor plant is located at the 148th Street repair shop, and another plant within the subway at 41st Street, for supplying air to the pumps, within the immediate locality of each compressor plant. For the more remote pumps, air will be supplied by smaller air compressors located within passenger stations. In one case, for the No. 2 sump, air will be taken from the switch and signal air-compressor plant located at the No. 11 sub-station. CHAPTER XI REPAIR AND INSPECTION SHED While popularly and not inaccurately known as the "Subway System," the lines of the Interborough Company comprise also a large amount of trackage in the open air, and hence the rolling stock which has already been described is devised with the view to satisfying all the peculiar and special conditions thus involved. A necessary corollary is the requirement of adequate inspection and repair shops, so that all the rolling stock may at all times be in the highest state of efficiency; and in this respect the provision made by the company has been lavish and liberal to a degree. The repair and inspection shop of the Interborough Rapid Transit Company adjoins the car yards of the company and occupies the entire block between Seventh Avenue on the west, Lenox Avenue and the Harlem River on the east, 148th Street on the south, and 149th Street on the north. The electric subway trains will enter the shops and car yard by means of the Lenox Avenue extension, which runs directly north from the junction at 142d Street and Lenox Avenue of the East Side main line. The branch leaves the main line at 142d Street, gradually approaches the surface, and emerges at about 147th Street. [Sidenote: _General Arrangement_] The inspection shed is at the southern end of the property and occupies an area of approximately 336 feet by 240 feet. It is divided into three bays, of which the north bay is equipped with four tracks running its entire length, and the middle bay with five tracks. The south bay contains the machine-tool equipment, and consists of eighteen electrically driven machines, locker and wash rooms, heating boilers, etc., and has only one track extending through it. [Sidenote: _Construction_]