sts of a pair of compound surface condensing engines, with
cylinders 11 in. and 20 in. in diameter; the shafting running the
whole length of the vessel, with a propeller at each end. Steam is
generated in a steel boiler of locomotive form, so arranged that the
funnel passes through the deck at the side of the vessel; and it is
designed for a working pressure of 100 lb. per square inch. This
boiler also supplies steam for the small hauling engine fixed on the
bulkhead. Light to this compartment is obtained by means of large side
scuttles along each side of the boat and glass deck lights, and the
iron grating at the entrance near the deck house. This boat was
constructed in six pieces for shipment, and the whole put together in
the builders' yard. The machinery was fixed, and the engine driven by
steam from its own boiler, then the whole was marked and taken
asunder, and shipped to the West Indies, where it was put together and
found to answer the purpose intended.--_Engineering._

* * * * *

[For THE SCIENTIFIC AMERICAN.]

THE PROBLEM OF FLIGHT, AND THE FLYING MACHINE.

As a result of reading the various communications to the SCIENTIFIC
AMERICAN and SUPPLEMENT, and _Van Nostrand's Engineering Magazine_,
including descriptions of proposed and tested machines, and the
reports of the British Aeronautical Society, the writer of the
following concludes:

That, as precedents for the construction of a successful flying
machine, the investigation of some species of birds as a base of the
principles of all is correct only in connection with the species and
habits of the bird; that the _general mechanical principles_ of flight
applicable to the _operation_ of the _same unit_ of wing in _all_
species are alone applicable to the flying machine.

That these principles of _operation_ do not demand the principles of
_construction_ of the bird.

That as the wing is in its stroke an arc of a screw propeller's
operation, and in its angle a screw propeller blade, its animal
operation compels its reciprocation instead of rotation.

That the swifter the wing beat, the more efficient its effect per unit
of surface, the greater the load carried, and the swifter the flight.

That the screw action being, in full flight, that of a screw propeller
whose axis of rotation forms a slight angle with the vertical, the
distance of flight per virtual "revolution" of "screw" wing far
exceeds the pitch dist