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

514 ELECTRIC TELEGRAPH CONDUCTORS.
The following is the result of some experiments mentioned
in the German works.
Silver........... 136 Platinum.................. 22
Gold....113 Iron..............17
Copper...................103 Mercury............ 2.6
Zinc..................... 28
This table is to be understood thus: a copper wire 100 feet
in length, offers as great a resistance in the transmission of an
electric current, as silver wire, of equal thickness, 136 feet
long; of gold 113 feet long; of iron 17 feet long, and so on with
the other metals.
Mr. Moses G. Farmer, of Boston, instituted thorough experiments, and the following were found to be the relative conductibility of the respective metals and fluids. The specific
resistance to the transmission of electric currents, compared
with chemically pure copper at ordinary temperatures, was, of
Copper wire............. 1.00 Tin wire............... 6.80
Silver "..............98 Zinc "............. 3.70
Gold "............ 1.13 Brass".. 3.88
Iron "............ 5.63 German Silver wire......11.30
Lead ".............10.76 Nickel "...... 7.70
Mercury..................50.00 Cadmium ".. 2.61
Palladium wire......... 5.50 Aluminum "...... 1.75
Platinum ".......... 6.78
His experiments with fluids produced the following results:
Pure rain water,.......... 40,653,723.00
Water twelve parts and Sulphuric Acid one........ 1,305,467.00
Sulphate Copper one pound per gallon,............18,450,000.00
Saturated Solution of Common Salt,.............. 3,173,000.00
Saturated Solution of Sulphate of Zinc......... 17,330,000.00
Nitric Acid 30~ B.,............... 1,606,000.00
CONDUCTING POWVER OF DIFFERENT SIZES OF COPPER WIRE.
Experiments showing the relative resistance of Nos. 18 and 16
copper wire, insulated by double covering of gutta-percha,
and submerged in the Regent's Canal, London.
No 18 gauge copper wire, covered with gutta-percha to gauge No. 7.
No. 16 gauge copper wire, covered with gutta-percha to gauge No. 4.
An ordinary single needle instrument was employed-connected to earth, as
usual in practice.
100 miles. No. 18. No. 16.
With 3 pairs of plates......29.......... 39~ deflection of needle
" 6'........50~........59~ "
The same instrument employed, but the needle slightly weighted:
Battery of 72 pairs plates. No. 18. No. 16.
100 l miles.......................23~................... 30~
90 "........25~.................
80 "..............26~..........
70...................28~....
65 ".............30~..................