With mournful voice, ever croaking low,
"Sing, happy birds!" says the old gray crow.

"Blest little birds! sing, for you may,
You do not die from home far away!"

       A GREAT SCREW.

When Mr. Hargreaves rode into Sydney
with a small piece of gold and quartz-rock
in his pocket, he could scarcely have
understood that he carried with him that which
would not only change the destinies of the
great Australian continent, but likewise effect
to a large extent a revolution in the commercial
relations of the whole civilised world.
And when, on the first of May eighteen
hundred and fifty-one —the very day on
which our Great Exhibition in Hyde Park
was opened —the Governor of New South
Wales penned his official sanction to the gold
explorer's further labours, neither of them
can have pictured a tithe of the mighty
results which were destined to originate from
that one epistle—

"What great events from trifling causes spring!"

Few things of moment have had more
insignificant beginnings than the screw
propeller for steam-ships; and few inventions
are destined lo produce more important
benefits, more especially in connection with the
great gold results which have sprung from
Mr. Hargreaves's trifling nugget. The
Australians can no more get on without the
potent aid of the screw, than they can do without
cradles, dampers, wide-awakes, Guernsey
shirts, and patent revolvers. The screw will
bring them within a fifty-five days' run of
home. The screw will drive their gold to the
markets of Europe more safely and
expeditiously than any other propeller. The screw
will enable their "made men" to reach the
mother courtry without a gale or a fit of
sea-sickness, by cheating both the much
dreaded Capes. The screw is, in fact, the
Australians' "coming machine."

Many of the most valuable scientific
improvements have been brought to light by
unexpected agencies. Amongst the hundred
and fifty patents which have been taken out
for various applications of the screw
propeller, may be found, in addition to the
names of engineers, machinists, ship-builders,
and other professional men, those of
ropemakers, farmers, printers, wharfingers,
merchants, soldiers, and noblemen; and it is
an undoubted fact that the most valuable
additions made to our stores of
screw-knowledge, have come from men uneducated
for, and unconnected with, any branch of
practical engineering. Whilst machinists and
civil engineers had for fifty years failed to
contrive any really practical adaptation of the
screw for propulsion, the laurels of screw
science were won, first in seventeen hundred
and ninety-four by a merchant, and since,
in eighteen hundred and thirty-six, jointly by
an English farmer and a Swedish military
officer.

The first attempt at screw propelling, which
in any degree realised its object, was that of
Mr. Lyttleton, a merchant of Goodman's Fields.
It was, however, too rude and inefficient for
practical purposes, and was laid aside with
scores of other useless projects which saw
the light between that period and the year
eighteen hundred and thirty-six. One single
exception to this array of failures is to be
found in the improvement of a Mr. Cummerow,
also a merchant of London; who, in
eighteen hundred and twenty-nine, placed the
screw between the stern of the ship and the
rudder-post, a principle which has been since
adhered to.

Early in the spring of eighteen hundred
and thirty-six, Mr. J, P. Smith, a farmer of
Hendon, obtained a patent for a new screw
propeller; and so well did he succeed in
working his first little model exhibited at
the Adelaide Gallery, that he obtained
assistance which enabled him to build and
fit up a small vessel of six tons. During the
month of November of the following year,
the screw-propelling farmer ventured out to
sea in his toy-ship; and proceeded boldly
down Channel, making excellent progress
through a stormy sea, and dead against the
wind. So complete was the triumph of the
screw, that all the scientific world were
convinced; and even the Admiralty found ears
to listen. A larger vessel was consequently
built, in which many of the naval authorities
made experimental trips to sea and round
the English coast; with such success, that
eventually Government formally adopted the
new propeller, and laid down the Rattler of
eight hundred and eighty-eight tons, to be
fitted with engines and a powerful and
improved screw. By this time an accident
which happened to the first wooden model,
demonstrated that a short screw, with narrow
fans, was better than a long screw with
broad fans; and the iron screw made for the
Rattler was of a double thread, but of only
one-sixth of a convolution. A year or two
later, the principle was so completely
established in the royal dockyards, that twenty
ships of war were fitted with auxiliary
screw-power.

While Smith had been thus active, Ericsson,
a Swedish officer, had also laid before
the authorities a screw of a novel construction;
but, however well this may have
been worked experimentally, the Government
were not at that time disposed to think
favourably of the new propeller, and Ericsson
carried his patent to the United States,
where he also improved on Stirling's hot air
engine, but only with partial success. The
latest and most valuable advance in the
construction of screw propellers, is that made by
Mr. Griffiths: which —by a modification of
the breadth of each section of the curved