TRANSACTIONS OF SECTION G. 84.7 
2. A very large percentage of the total weight (or displacement) of a torpedo 
vessel is assigned to propelling apparatus. In a destroyer of 30 knots trial-speed, 
nearly one-half the total weight is devoted to machinery, boilers, &c. In the 
swiftest cruisers of large size the corresponding allocation of weight is less than 
20 per cent. of the displacement, and in the largest and fastest mail steamers it is 
about 20 to 25 per cent. 
3. The torpedo vessel carries a relatively small load of fuel, equipment, &c. 
Taking a 30-lnot destroyer, for example, the speed trials are made with a load not 
exceeding 12 to 14 per cent. of the displacement. In a swift cruiser the corre~ 
sponding load would be from 40 to 45 per cent., or proportionately more than 
three times as great. What this difference means may be illustrated by two 
statements. If the load in a destroyer were trebled and the vessel correspondingly 
increased in draught and weight, the speed attained with the same maximum 
power would be about three knots less. If, on the other hand, the vessel were 
designed to attain 30 knots on trial with the heavier load, her displacement 
would probably be increased about 70 to 80 per cent. 
4, The hull and fittings of the torpedo vessel are exceedingly licht in relation 
to the dimensions and engine-power. For many parts of the structure steel of 
high teusile strength is used. Throughout, the utmost care is taken to economise 
weight. In small vessels, for special service, many conditions can be accepted 
which would be inadmissible in larger sea-going vessels. The result of all this 
care is the production of hull-structures having ample general strength for their 
special service. Lightness of scantling, of course, involves small Jocal strength 
against collision, grounding, and other accident. Experience proves, however, 
that this involves no serious risk or difficulty. 
These conditions are essential to the attainment of very high speeds for short 
periods. They resemble the conditions ruling the design of cross-Channel steamers, 
so far as relative lightness of propelling apparatus, small load, and light scantlings 
are concerned. The essential differences lie in the requirements for passenger 
accommodation as compared with the requirements for armament of the torpedo 
vessel. No one has yet proposed to extend the torpedo-vessel system to sea-going 
ships of large dimensions. Very similar conditions for the propelling apparatus 
have been accepted in a few cruisers of considerable dimensions, wherein high 
speeds for short periods were required. It is, however, unquestionable that in 
many ways, and particularly in regard to machinery design, the construction of 
torpedo vessels has greatly influenced that of larger ships. 
One important consideration must not be overlooked. For short-distance 
steaming at high speeds economy in coal consumption is of little practical 
importance, and it is all-important to secure lightness of propelling apparatus in 
relation to power. For long-distance steaming, on the contrary, economy in coal 
consumption is of primary importance; and savings in weight of propelling 
apparatus, even of considerable amount, may be undesirable if they involve 
increased coal consumption. Differences of opinion prevail as to the real economy 
of fuel obtainable with boilers and engines such as are fitted in torpedo vessels. 
Claims are made for some vessels which represent remarkable economy. Only 
enlarged experience can settle these questions. 
Endurance is also an important quality in sea-going ships of large size, not 
merely in structures, but in propelling apparatus. The extreme lightness essential 
in torpedo vessels obviously does not favour endurance if high powers are frequently 
or continuously required. Still, it cannot be denied that the results obtained in 
torpedo vessels show such a wide departure from those usual in sea-going ships as 
to suggest the possibility of some intermediate type of propelling apparatus 
applicable to large sea-going ships and securing sufficient durability and economy 
of fuel in association with further savings of weight. 
The Parsons Turbo-Motor. 
~ The steam turbo-motor introduced by Mr. Charles Parsons is to’ be described 
by the inventor during these meetings ; but it is impossible for me to pass it over 
