357 OF ENGINEERING FORMULÆ.
Telegraph Construction, by Paget Higgs, LL.D.,C.E.
—continued.
Single Sheathing: X -7854 X kn (Table A)
less D2 X -7854, where d is diameter single iron
wire and D is diameter of core, n number ot wires.
Double Sheathing: x*7g54 x knj (^a^le
less f 7 1 (TaMe B). Then as
less <j,2 x -7854 X kn) v 7
1 cwt. of Itai, or Russ, hemp = 4928 cub. in.,
tarred hemp = 3472 cub. in., and as there are
73044 cub. in. iu a knot length of 1" sectional
(73014 \
•49^8 - 14 ’822’ &c,)‘
Area of hemp/ X 14-822 = cwts. Itai, hemp
section in inchest, per knot.
X 21'038 = tarred hemp per
knot.
X 15-528 = Manilla hemp per
knot.
Area in square mm. X ‘0230 = cwts. Itai, hemp
per knot.
X • 326 — cwts. tarred hemp
per knot.
X *0241 = cwts. Manilla
lu mp per knot.
Asphalte casing (outer diam.) 2 X '7854 less
d2 Jen (Table B) gives area.
And this iu sq. in. X 36 = cwts. asphalte per knot,
mm. X '0558 = cwts. asphalte per
” Irr» rd-
Area in sq. mm
mm. X 3’3928 = kilos, per knot.
. x 1'1685 = kilos. Itai. hemp.
' x 1-6561 = „ tarred „
X 1-2243 = „ Manilla „