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

592 SUBTERRANEAN TELEGRAPHS.
through semi-circular lugs projecting about one and a half
inches from the side; one pair of lugs being about nine inches
fiom the faucet, and another pair two feet from the spigot end.
A pipe of these dimensions is cheaper than the old threeinch solid pipe, and more generally useful, the halves being
convenient, for fixing to walls, viaducts, &c., over wires needing good protection in such places; and, from its circular form
and smallness, it is very difficult to break, as a pick-axe, or
other tool, cannot easily strike it full.
The process of laying in the wires is rendered much more
texpeditious and economical by the use of half pipes. The
under halves of the pipes are laid down in the trench, and then
a large drum, on which the insulated wires are wrapped, is
rolled along over the trench, and the wire is paid off easily
and rapidly into its place-the upper parts of the pipes put on
afterward, and secured in their places by means of screws
through small flanges, left outside for the purpose.
So well has this mode succeeded, that in Liverpool the
whole lengths of the streets, from Tithebarn railway station to
the office in Exchange-street east, were laid down in a single
night (eleven hours), and in Manchester, the line of streets
from the railway station in Salford to Ducie-street, by the
Manchester Exchange, in twenty-two hours. This was the
whole time occupied in opening the trenches, laying down the
telegraph wires, and re-laying the pavement.
Mr. Reid has invented an ingenious modification of the half
pipe, of the rectangular form, which he has patented, and
which we have used. Mr. Henley also has improved on the
circular half pipe where it is intended only for subterranean
work, which he has also patented; but both of them have top
and under lengths differently shaped, and I find my original
plan preferable for general purposes. All the telegraph companies have adopted the two-piece pipe in place of the solid
round pipe, except the old company. The depth of trench is
two feet, but all obstacles, as drains, &c., are passed under.
I have had no experience in laying underground wires with
single-covered gutta-percha, having, in common with all telegraphic engineers in this country considered the occasional
small flaws and air bubbles which occur in single wire, and
which are covered and made good by the second coating, a bar
to its use, except about stations, &c., where it is not in close
contact with the earth, and may be readily examined.
I do not think wire, covered with hemp only, could ever be
laid so as to preserve good insulation, equally with that coated
properly with gutta-percha.