Whether true or not generally, it was demonstrated in young Edison and it governed his learning telegraphy and the manner thereof.

"Mr. Edison likes to tell of the prevailing ignorance of the science of telegraphy.

WIRELESS TELEGRAPHY ESTABLISHED XVIII.

The perfection of wireless telegraphy has caused the Ardois and other signal systems depending upon sight or sound to be discarded in all but exceptional cases.

The wig-wag and similar systems will probably never be entirely displaced by even such superior systems as wireless telegraphy.

About this time two professors at the University of Göttingen were experimenting with telegraphy.

Davy's greatest contribution to telegraphy was the relay system by which very weak currents could call into play strong currents from a local battery, and so make the signals apparent at the receiving station.

Thus but two characters had been used, or one-half cent's worth of telegraphy.

Though men of larger means refused to take shares, some in humbler circumstances could recognize the great idea and the wonderful vision which Morse had struggled so long to establisha vision of a nation linked together by telegraphy.

This was called duplex telegraphy.

Edison invented duplex telegraphy by which two messages could be sent over the same wire in the same direction at the same time.

It is recorded that a Spaniard suggested submarine telegraphy in 1795.

These gutta-percha-covered wires were used for underground telegraphy both in England and on the Continent.

Professor Thomson had been studying the problems of submarine telegraphy with growing enthusiasm, and had now arrived at the conclusion that the conductivity of the cable depended very largely upon the purity of the copper employed.

Such was the greatest contribution of Professor Thomson to submarine telegraphy.

Professor Thomson was to give to submarine telegraphy an even more remarkable instrument.

But in addition he was picking up some knowledge of anatomy, music, electricity, and telegraphy.

His experiments with telegraphy and telephony had been laid aside, and there seemed little chance that he would turn from the work in which he was accomplishing so much for so many sufferers, and which was bringing a comfortable financial return, and again undertake the tedious work in search for a telephone.

" From that time forward Hubbard took every occasion to encourage Bell to carry forward his experiments in musical telegraphy.

But Bell's greatest contribution to the search for wireless telegraphy was not his direct work in this field, but the telephone itself.

Prof. John Trowbridge, of Harvard University, might well be termed the grandfather of wireless telegraphy.

Telegraphy through the earth was thus possible.

It occurred to him that by their aid wireless telegraphy might be accomplished.

Each week he expected the news that wireless telegraphy had been established, but the news never came.

To make wireless telegraphy effective over any considerable distance a highly efficient and extremely sensitive receiving device is necessary.