For instance up to about two hundred miles a storage battery and
induction coil are sufficient to produce the necessary ether
disturbance, but when a greater distance is to be spanned an engine
and a dynamo are necessary to supply energy for the electric waves.

In the most recent Marconi transmitter the current produced is no
longer in the form of intermittent sparks, but is a true alternating
current, which in general continues uniformly as long as the key is
pressed down.

There is no longer any question that wireless telegraphy is here to
stay. It has passed the juvenile stage and is fast approaching a lusty
adolescence which promises to be a source of great strength to the
commerce of the world. Already it has accomplished much for its age.
It has saved so many lives at sea that its installation is no longer
regarded as a scientific luxury but a practical necessity on every
passenger vessel. Practically every steamer in American waters is
equipped with a wireless station. Even freight boats and tugs are
up-to-date in this respect. Every ship in the American navy, including
colliers and revenue cutters, carries wireless operators. So important
indeed is it considered in the Navy department that a line of shore
stations have been constructed from Maine on the Atlantic to Alaska
on the Pacific.

In a remarkably short interval wireless has come to exercise an
important function in the marine service. Through the shore stations
of the commercial companies, press despatches, storm warnings, weather
reports and other items of interest are regularly transmitted to ships
at sea. Captains keep in touch with one another and with the home