G.—ENGINEERING. 137 
which is still something of a mystery ship. Except for this rare and as 
yet unfledged bird, naval usage sticks to steam. 
But the mercantile marine is in a state of flux. Before the War there 
were almost no motor-driven ships. Vigorous efforts had been made 
to promote the use of gas-engines with producer-gas made on board as 
it was required, but these achieved no permanent success. The Selandia, 
which dates from 1912, was the first conspicuous example of a large ship 
driven by Diesel engines. Her economy of fuel at once commanded 
attention. She was naturally hailed with delight by the powerful oil 
interests whose position, already strong in the mercantile marine through 
the extended use of oil under boilers, would become impregnable if the 
Diesel engine were generally adopted. In some important quarters the 
Diesel engine became the vogue. During the post-War years of marine 
reconstruction the number of oil-driven motor-ships rapidly increased, and 
it is still increasing. In 1930, according to Lloyd’s Register, the gross 
tonnage of the world’s shipping was in round figures 69} million tons, of 
which 13 million were survivors from the ancient régime of sails. Of the 
68 million tons that were mechanically propelled 60 million tons were 
steam-ships and 8 million tons were motor-ships. The motor tonnage had 
increased nearly four-fold in the preceding three years. Of merchant 
vessels launched during the year 1930, considerably more than half the 
tonnage was motor-driven ; and even in Great Britain the motor tonnage 
launched in that year was nearly 52 per cent. of the whole tonnage launched. 
For the moment the motor-ship is in the ascendant. At this rate, a 
superficial observer might fancy that steam was in process of being driven 
off the high seas. But if that were his conclusion I think he would be 
quite wrong. 
Tf you look at the list of shipping in detail .you will notice several 
things. One is that none of the greatest and fastest ships are motor- 
_ driven—neither the Leviathan, which at present heads the list, nor any 
of the other leviathans of the deep, with their tonnages of 40,000 or 50,000 
tons or more, and their speeds ranging from 20 to 28 knots. And this is 
true not only of the older ships but also of the newest, such as the Europa 
and the Bremen and the Empress of Britain, and the giant Cunarder which 
is now on the stocks and is confidently expected to eclipse them all. For 
_ such vessels, motors do not give the concentration of power that is needed 
whereas turbines do give it, and give it easily. From Lloyd’s list of marine 
engines under construction at the end of March, 1931, I find that the 
average shaft-horse-power of the (51) turbines is nearly 20,000, whereas 
that of the (328) motors is not much over 2,000. The present fashion, 
if one may call it so, is to put motors into ships of moderate size and 
‘power. The same list gives 189 as the number of reciprocating steam- 
engines under construction; these are mainly for comparatively small and 
slow ships, for their average horse-power is of the order of 1,000. The 
ocean tramp is perhaps regrettably conservative in the manner in which 
she uses steam, but for ships of larger power the advantage of the turbine 
is too conspicuous to be ignored. 
Of motor-driven ships many are tankers, a type that has been called 
into existence by the world’s demand for transport of oil in bulk, both 
for internal-combustion engines and for burning under boilers. Of 
to 
