of steel scrapers, somewhat like those used in cleaning boilers. The
device is put into the pipe, and propelled by the pressure transmitted
from the pumps from one station to another; relays of men follow the
scraper by the noise it makes as it goes through the pipe, one party
taking up the pursuit as the other is exhausted. They must never let it
get out of their hearing, for if it stops unnoticed, its location can
only again be established by cutting the pipe.

The pumping stations are substantial structures of brick, roofed with
iron. The boiler house is removed some distance from the engine house
for greater safety from fire; the building, about 40 by 50 feet,
contains from six to seven tubular boilers, each 5 by 14 feet, and
containing 80 three-inch tubes. The pump house is a similar brick
structure about 40 by 60 feet, and contains the battery of pumping
engines to be described later. At each station are two iron tanks, 90
feet in diameter and 30 feet high; into these tanks the oil is delivered
from the preceding station, and from them the oil is pumped into the
tanks at the next station beyond. The pipe-system at each station is
simple, and by means of the "loop-lines" before mentioned the oil can be
pumped directly around any station if occasion would require it.

The pumps used on all these lines are the Worthington compound,
condensing, pressure pumping engines. The general characteristics of
these pumps are, independent plungers with exterior packing, valve-boxes
subdivided into separate small chambers capable of resisting very heavy
strains, and leather-faced metallic valves with low lift and large
surfaces. These engines vary in power from 200 to 800 horse-power,
according to duty required. They are in continuous use, day and night,
and are required to deliver about 15,000 barrels of crude oil per 24
hours, under a pressure equivalent to an elevation of 3,500 feet.