machinery, water, and fuel carried for propelling ships has not had due
attention in the general practice of engineers. By the best shipping
authorities the writer is assured that every ton of dead weight capacity
is worth on an average L10 per annum as earning freight. Assuming,
therefore, the weight of the machinery and water of any ordinary vessel
to be 300 tons, and that, by careful design and judicious use of
materials, the engineer can reduce it by 100 tons, without increasing
the cost of working, he makes the vessel worth L1,000 per annum more to
her owners. That there is much room for improvement in this direction is
shown by the following statement, giving, for various classes of ships,
the average weight of machinery, including engines, boilers, water, and
all fittings ready for sea, in pounds, per indicated horse power:

Lb. per I. H. P.

Merchant steamers.......................... 480
Royal Navy................................. 300
Engines specially designed for light draught
vessels...................................280
Royal Navy, Polyphemus class (given by Mr.
Wright).................................. 180
Modern locomotive.......................... 140
Torpedo vessels............................. 60

Ordinary marine boilers, including water... 196
Locomotive boilers, including water......... 60

The ordinary marine boiler, encumbered as it is by the regulations of
the Board of Trade and of Lloyds' Committee, does not admit of much
reduction in the weight of material or of water carried when working.