G.—ENGINEERING. 139 
of, published facts about the cost of upkeep with Diesel engines. Prima 
facie, the great number of reciprocating parts is a serious drawback. There 
must be a great number because the safe limit of cylinder size is soon 
reached, and it is only by having many cylinders that any large aggregate 
of power is developed. In a recent Diesel-engined liner of the luxurious 
type, a ship of some 17,000 or 18,000 tons, 12 Diesel cylinders operate 
on each of four shafts, making 48 in all, to produce a speed of 18 to 20 
knots. Besides these 48 main cylinders, there are 24 more which serve 
purposes that are auxiliary but essential to the working of the main 
engines. Consider the number of working joints, of valves, of valve- 
rods and tappets, besides pistons and connecting-rods, which this involves, 
Does such an accumulation of reciprocating pieces with their hammer- 
blow accelerations mark a real engineering advance as compared with 
the cosy hum of a turbine engine room, and has it come to stay ? Frankly, 
I think not. 
As a last technical point I would say a few words about fuel for marine 
engines. Can anything be done to re-establish the ancient connection of the 
merchant service with the British coalfields? Remember that here and 
in most other places, the cost of coal is substantially less than that of oil, 
for the same quantity of heat. Where oil scores is in its greater con- 
venience of handling. Much has been said and written about restoring 
prosperity to the miners by converting coal into oil. As a chemical 
_ operation, it is quite possible to make oil from coal ; as a commercial propo- 
_ sition, it is impracticable, so long as nature continues to supply oil directly 
_ from the bountiful stores on which man now draws with careless and pro- 
 digal ease. Ships that burn oil must have it come to them from sources 
outside Great Britain. Well, then, can we expect ships to return to the use 
of coal as fuel? For some classes of ships I think we may, though not all 
_ classes. Neither in the navy nor in what one may call the upper division of 
_ the mercantile marine—the luxurious express liners which carry 
fastidious passengers and must keep to a time-table that means quick 
_ fuelling—can one expect a reversion to coal so long as oil fuel can be got at 
anything like its present price. But with cargo-liners and big cargo-boats, 
_ the case is different. They do offer a possible field for the use of coal, a field 
where I believe its use would be economically sound as well as of great 
“national advantage. In the running of such ships, the incidental con- 
-yenieuces of oil fuel count for less. The cost of fuel is a relatively big 
factor and there is a clear advantage in being able to burn either coal 
or oil at option, according to the local cheapness of supply. There the 
_ geared turbine with coal fuel can more than hold its own provided the 
steam plant embodies the conditions that make for high efficiency, 
conditions which are now known to be attainable in marine practice. 
a] think those engineers are right who contend that for such ships a highly 
economic mode of working would be to use pulverized coal for steam- 
Taising in a small number of large boilers of the water-tube type, with 
iow p of say 500 lb. and a temperature of 750° ¥., each boiler having 
its own pulverizing mill and being fitted also for burning oil as an alterna- 
ve fuel. In such a scheme, there would be no untried elements, but the 
~ combination of the elements would be experimental, and a conclusive 
demonstration of its advantages can be obtained only by testing it out 
