mount of room as if paddles had been used, and the
result will be much the same as if paddles had been adopted. When
direct acting engines, however, are employed, the machinery will
occupy a much less space in screw vessels than is possible in paddle
vessels, and the use of direct acting engines in screw propellers is
necessary, therefore, for the realization of the full measure of
advantage, which screw propulsion is able to afford."

Atherton says of the propeller in his "Marine Engine Construction and
Classification," page 45:

"Its operation has been critically compared with that of the
paddle-wheel, under various conditions of engine power, and experience
has shown that, under circumstances which admit of the screw propeller
being favorably applied, it is equal to the paddle-wheel as an
effective means of applying engine power to the propulsion of the
vessel." Again:

I recently addressed to Mr. Atherton the following question: "Taking
two ships of the same _size, displacement, and power, or coal_, the
one a side-wheel, the other screw: What will be their relative _speed
and carrying capacity_ in smooth water? What in a sea-way, or in
regular transatlantic navigation?" He replied under address, "Woolwich
Royal Dock Yard, 14 Sept., 1857:

"It is my opinion, based on experiment, that a well-applied screw is
quite equal to the paddle-wheel for giving out the power by which it
is itself driven, that is, in smooth water. I can not say from
observation or experience what is the comparative operation at sea."

I addressed the same inquiry to Mr. Robert Murray, of Southampton, who
has written an able work, entitled, "The Marine Engine," and who is
considered excellent authority, and have from him the following reply,
dated Southampton, 19 Sept., 1857:

"With regard to the relative efficiency of the paddle-wheel and screw
for full-powered mail steamers, I am disposed to prefer the
paddle-wheel for _transatlantic_ steaming, in which the vessel has to
contend with so much rough weather and heavy sea, and the screw for
the Mediterranean and the Pacific routes.

"For auxiliary steamers of any kind the screw has manifestly the
advantage.

"With regard to the actual speed obtained from each mode of propulsion
in vessels of the same power and form, and with the propeller in its
best trim, I am disposed to prefer the paddle-wheel, either in smooth
water, or when steaming head to wind, but in other conditions the
screw."