ney towards its solution previous to 1900, it was only
after that year that governmental interest and influence were set to
work with determination and purpose on behalf of submarine inventors.
Quite naturally this resulted in increased popular interest.
Experimental work on and with submarines no longer had to rely
exclusively on private capital, frequently inconveniently timid and
limited, but could count now on the vast financial resources of all
the great nations of the world. This also made available the unlimited
intellectual resources of serious scientists in every part of the
universe. Mechanical and electrical engineers, naval designers and
constructors, active men of finance and business, and quiet thinkers
and investigators in laboratories began to interest themselves in the
further development of the submarine.

The United States for a number of years after its adoption of the
Holland type remained true to its first choice. Between 1900, when
the first Holland boat was bought by the United States Government,
and 1911 all the United States submarine, boats were of the Holland
type. In the latter year, however, it was decided to give the Lake
boat a trial and since that time a number of boats of this type have
been built. In all essential features both the Holland and Lake
boats of later days were very similar to the original boats of these
two types. In all the details, however, immense progress was made.
Each new boat thus became greatly superior to its predecessors. This
was especially true in regard to size and speed and the improvements
made in these two respects naturally resulted in a corresponding
increase in radius of activity. The passing years also brought a
wonderful refinement of all the technical details of the submarine
boats. Practically every feature was developed to a remarkable
degree. There is, indeed, a great difference between the submarine
boats of the early twentieth century which had to rely on their
conning-tower for steering, and more recent boats with their
wonderful periscopes and gyro compasses. Similar progress was made
in the development of the means of propulsion. The engines used for
surface travelling became more powerful and efficient. This was also
true of the electric motors, batteries, and accumulators employed
in the submerged state. The problem of ventilation likewise has been
worked out to such an extent that in the most modern submarines most
of the inconveniences ex