was 4-inch, with the usual steam thread, but the joints leaked under the
pressure, 1,200 pounds to the square inch being the maximum the 8-thread
pipe would stand. This trouble has been remedied by the 9-thread,
taper-cut pipe of the present day, which is tested at the mill to 1,500
pounds pressure, while the average duty required is 1,200 pounds; as the
iron used in the manufacture of this line-pipe will average a tensile
test strain of 55,000 pounds per square inch, the safety factor is thus
about one-sixth.

[Illustration: PROFILE SHOWING NATIONAL TRANSIT CO.'S PIPE-LINE, FROM
OLEAN TO SADDLE RIVER.]

The line-pipe is laid between the stations in the ordinary manner,
excepting that great care is exercised in perfecting the joints. No
expansion joints or other special appliances of like nature are used on
the line as far as we can learn; the variations in temperature being
compensated for, in exposed locations, by laying the pipe in long
horizontal curves. The usual depth below the surface is about 3 feet,
though in some portions of the route the pipe lies for miles exposed
directly upon the surface. As the oil pumped is crude oil, and this as
it comes from the wells carries with it a considerable proportion of
brine, freezing in the pipes is not to be apprehended. The oil,
however, does thicken in very cold weather, and the temperature has a
considerable influence on the delivery.

A very ingenious patented device is used for cleaning out the pipes, and
by it the delivery is said to have been increased in certain localities
50 per cent. This is a stem about 21/2 feet long, having at its front end
a diaphragm made of wings which can fold on each other, and thus enable
it to pass an obstruction it cannot remove; this machine carries a set