lowed some six weeks later, or on July 13, 1836. While it thus
appears that Ericsson had been studying the problem since 1833 or
earlier, according to his own statements, there is no evidence that
Smith's attention was drawn to the matter earlier than 1835. Delay on
Ericsson's part in the matter of patent gives the earlier date to Smith.
The mere date of a patent, however, is of small moment for our present
purposes. It must be admitted that the modern form of screw-propeller is
quite unlike either of these original forms, although they all involve
of course the same fundamental principles. Ericsson's propeller may
properly be called an engineering success, built on sound principles,
but improved and largely modified by the results of later experience and
research. Smith's propeller, while capable of propelling a boat, was the
design of an amateur rather than of an engineer, and in comparison with
Ericsson's seemed to show a somewhat less accurate appreciation of the
underlying principles upon which the propeller operates.

In the present case, as we have noted above, the question is not so much
one of invention as of influence in introduction, adaptation, and
improvement. The screw-propeller was already known, but had not been
introduced into and made a part of actual engineering practice. Services
in this direction are all that can be claimed for any of those concerned
with the question during the third decade of the Nineteenth Century.
From this point of view we must give to Ericsson large credit. He had
the courage of his convictions, and did not allow his work in this
direction to lapse for lack of effort on his part to secure its
introduction into the practice of the day.

Thus, in 1837, the "Francis B. Ogden" was built for the special purpose
of testing the power of the screw-propeller, and was operated on the
Thames for the benefit of the British Admiralty and many others. Shortly
after this, and largely through the influence of Capt. Robert F.
Stockton of the American Navy and Francis B. Ogden, the American Consul
at Liverpool, Ericsson began to consider a visit to the United States
for the purpose of building, under Stockton's auspices, a vessel for the
United States Navy. While these negotiations were under way, in 1838, he
built for Captain Stockton a screw-steamer named the "Robert F.
Stockton," the trials of which attracted much attention from the public
at large and from engineers of the time. At about th