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Updated: May 5, 2025
In other words, if light is an electro-magnetic disturbance, all conducting substances must be opaque, and all good insulators transparent. This we know to be the fact: metallic substances, the best of conductors, are opaque, while glass and crystals are transparent.
Assembled Wireless Receiving Sets. It costs $15.00, and can be bought of dealers in electric supplies generally. This price also includes a crystal detector, an adjustable tuning coil, a single telephone receiver with head-band and the wire, porcelain insulators, lightning switch and ground clamp for the aerial wire system.
There the track being exclusively for the electric railway, it was not necessary to provide a center channel; the conductor has therefore been placed in the center of the track, and consists of bar iron 1¼ in. by ½ in., and is held vertically by means of studs riveted into the side; these studs pass through porcelain insulators, and by means of wooden clamps and wedges are held in the iron chairs which rest upon the sleepers.
Everything was crude and primitive. The poles were two hundred feet apart and could barely hold up a wash-line. The slim, bare, copper wire snapped on the least provocation, and the circuit was "down" for thirty-six days in the first six months. The little glass-knob insulators made seductive targets for ignorant sportsmen.
On either side innumerable huge Leyden jars stood ranged in rows, tier topping tier, while above them were columns of Voltaic cells. Robert's eyes, as he glanced around, lit on vast wheels, complicated networks of wire, stands, test-tubes, coloured bottles, graduated glasses, Bunsen burners, porcelain insulators, and all the varied debris of a chemical and electrical workshop.
In the case of the line to Fort Tregantle I spent a day with others on a fatigue party digging a trench across the road in which the cable was to be buried. A call went out to the local populace asking for empty cotton reels; these were to be used not specifically as insulators but rather as attachment points offering less fretting to the cable than a nail alone would do.
In this work they took due consideration of the professional objection to tree entanglements in aerials so that the insulators were well beyond the reach of the longest limbs. "It's a simple matter now to bring the outfit ashore and hook it up with the aerial," said Hal. "Let's do it." Enthused by the novelty of their enterprise, they continued the work, even though dusk was rapidly gathering.
When first the telegraph line from Derby to Hall's Creek and thence to Wyndham was constructed, constant damage used to be done to it by the natives who climbed the poles and smashed the insulators for spear-head making.
"We shall want 40,000 insulators they will cost from $6 to $8 per 100; 35,000 red cedar top pins will cost $3 per 100; 40 sets of telegraph instruments at $60 per set; main and local batteries, $500.
To be sure, the entire aerial was not packed, but merely the wires and insulators, as spreaders could be made in the forest. Then there was an additional coil of wire to be used for lead-in and suspension wires. No tuning instrument was necessary, because the wireless outfits of all the members of the Camp Brady Wireless Patrol were exactly alike and so were already in tune with one another.
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