The telegraph manual: a complete history and description of the semaphoric, electric and magnetic telegraphs of Europe, Asia, Africa, and America, ancient and modern.

DURABILITY OF TELEGRAPH POLES. 683
nor does it have so great quantity of sap. The bark is generally thin, and the sappy or white wood, is but a thin belt
around the interior heart or dark wood. Woodmen do not
consider all the dark wood beyond the sappy part the heart. For
example, take an oak-tree, two feet in diameter, a size very
ordinary in America, and first is the bark, then the sappy or
white wood belting the tree, about three inches in diameter,
then follows the dark, or red chip, until the heart is reached,
which is generally in the centre of the tree. This heart is solid
and tough. The dark or red wood is penetrated by sap. In
some seasons of the year, I have noticed, when felling the oak,
the walnut, and many other kinds of timber, the sap to run in
little streams from the white and the red wood alike. The
post-oak is much like white-oak, but it is a tree of slow growth,
and is to be found mostly on dry and gravel uplands. It is
more durable than the white-oak, in the earth. Cedar and
locust have but very little sap, and the fibres are closely interwoven, so that there can be but little absorption. It is a saying, that " cedar and locust never decay." These woods can
be regarded as the most durable that we have in America.
Poles, ten inches in diameter at the base, will remain good,
thirty or forty years in the earth. If the bark is left on the
pole, it will sooner or later decay, and the solid wood is left,
and weathers the storms and seasons for a lifetime. All kinds
of wood will be more durable when stripped of the bark. Chestnut and sassafras will hold out from ten to fifteen years.
White-oak, post-oak, honey-locust, ash, and black-walnut, about
six to ten years. White-pine and poplar, about three years;
black-oak, red-oak, and sycamore, about two years. All kinds
of fruit-tree wood, one to two years. The pitch or yellow pine
pole is quite durable in the earth. The turpentine or rosin does
not ferment, but it forms a plastic throughout the timber, and
prevents the absorption of moisture, and thus it is preserved
from decay. Much of the rosin, when the pole is exposed to the
sun, oozes out, and the exterior of the pole becomes coated
with it.
The durability of the different kinds of timber mentioned,
when used for telegraph poles, depends much upon the soil in
which they are set. When planted in light alluvial soil, the
decay is much more rapid than when placed in wet clay. In
the former case, worms easily get through the earth to the
pole, and, besides, the pole is more exposed, and absorbs the
moisture of the earth with more rapidity; but, in the latter
case, the clay serves as a plaster, filling up the cavities of
the wood, so that water cannot penetrate it. In such earth,