472 
NATURE 
fAPRIL-7, 1923 

and a half million tons. Shipowners have the choice 
of a dozen types of Diesel engines, such as the Bur- 
meister and Wain, the Werkspoor, the Sulzer, the Beard- 
more, the Cammellaird-Fullagar, and the Doxford, 
some being of the four-cycle and some of the two-cycle 
type. These engines differ in many respects, but all 
have the same characteristic in being more economical 
than the steam engine. Mention may also be made of 
the experiment being carried out with the Still engine, in 
which the top of the piston is acted upon by the pressure 
of the burning gases, while the underside is acted upon 
by the pressure of steam raised in a small boiler heated 
by the exhaust gases. 
In addition to the advocates of the steam turbine 
and the Diesel engine there is yet another school of 
engineers which believes the future of marine propulsion 
lies with what is known as the electric drive. This 
system has been developed far more in America than 
on this side of the Atlantic, and all recent capital 
ships for the United States Navy have electric trans- 
mission. In these vessels oil-fired boilers supply 
steam to Curtis turbines driving electric generators 
which supply current to the motors on the propeller 
shafts. ~The general adoption of such a system, it 
was pointed out by Prof. Abell, may lead to remarkable 
alterations in the plans of ships, as the engine-rooms 
can be placed between decks or otherwise as thought 
most suitable. A turbine-electric plant involves the 
use of boilers, turbines, condensers, generators, and 

motors, but an alternative is to replace the boilers, 
turbines, and condensers by Diesel engines. The 
various proposals have been reviewed in his book on 
“Electric Ship Propulsion’? by Commander S. M. 
Robinson, of the United States Navy. He there 
divides both naval and mercantile vessels into classes, — 
and states which type of machinery he considers most 
suitable. For the cargo tramp he would have Diesel 
engine and electric drive, for other merchant vessels 
and for large war vessels steam turbines and electric 
drive, while for destroyers and light cruisers he would 
retain geared turbine. 
From the foregoing it will be seen that the whole 
practice of marine engineering is, as it were, in the 
melting-pot, and what the standard form of marine 
propulsion will be in the future is difficult to see. 
Given trustworthiness, it is economy which has the 
deciding influence ; economy in weight, economy in 
space, economy in upkeep, economy in fuel. What 
the continual striving after economy has done in the 
past can be judged by the fact that, fifty years ago, to 
convey a hundred tons of cargo a mile required 18 to 
20 lbs. of coal ; to-day the same result is obtained with 
14 to 2 lbs of oil. Finality was thought by some to 
have been reached when the compound engine was intro- 
duced. Great advances have been made since then, 
But while it may not be possible to effect revolutions 
on the scale of the past, the time is far distant when 
improvements will be impossible. 
Obituary. 
Sir JAmes Dewar, F.RS. 
~IR JAMES DEWAR died at the Royal Institu- 
~? tion, in his eighty-first year, on March 27. He 
had been working in his laboratory until late on the 
night of March 20 and was taken ill in the early hours 
of the following morning. 
Our scientific edifice is thus suddenly deprived of 
one of its main pillars ; we shall not easily appraise the 
loss. The immensity and sustained originality of his 
genius, the service he rendered to our civilisation, can 
be but insufficiently appreciated outside the small 
circle of intimates who witnessed his work and, having 
penetrated through the thick mask of modesty and 
reticence which he habitually wore, could disregard his 
sometimes brusque, inconsequent manner, his volcanic, 
torrential outbursts of picturesque criticism—knowing 
these to be but the expression of an extreme intensity 
of conviction and purpose and an overmastering 
honesty. At heart he was full of human sympathy, a 
most gentle and lovable nature—but the presbyter was 
ever in him. 
As an experimentalist Dewar stood alone: there has 
never been a greater, probably none so great. Science 
loses in him a worker of peculiar breadth of originality, 
a most fascinating character ; how much the world is 
poorer it little knows. He was of a type—almost 
primitive, in this competitive age, in honesty of pur- 
pose—now fast becoming extinct, a lineal descendant 
of his great countryman, Joseph Black, in no way less 
successful than his predecessors, Young, Davy and 
Faraday, in adding to the reputation these pioneers 

discovery and invention. He also made it a social 
centre of great attraction and cast over it an <esthetic 
spell which it had not previously known. Davy 
sought society but did not fashion it. Dewar could 
rarely be persuaded into it but became himself noted 
as a host, on account of his own great conversational 
power and the beauty of the surroundings he accumu- 
lated : his home was the salon of science and art. 
As a lad Dewar met with an accident which, in after 
life, he regarded as fortunate. Falling through the 
ice, he contracted rheumatic fever and was long unable 
to attend school but became intimate with the village 
joiner. In those days, Scotland having been in close 
commercial relation with Italy, fiddles abounded and 
the lad had musical tastes. With his own hands he 
made several violins, from one of which we heard the 
sweetest of music conjured forth, by a skilled lady per- 
former, on the occasion of the celebration of his golden 
wedding, less than two years ago. He always regarded 
the training he thus received as the most important 
part of his education and the foundation of the great 
manual dexterity which he displayed in his work and 
his lectures. He often complained to me of the sad 
lack of such ability in the modern student. His master 
in chemistry was Lyon Playfair. Dewar was one of 
the few who could appreciate Playfair’s great scientific 
ability and were able to gauge the loss of his early 
deflexion into the tortuous paths of politics, which 
Playfair himself regretted in later life. The two men 
became fast friends and Playfair was long chief admirer 
of his pupil’s brilliant ability. At one time, I believe, 
Playfair endeavoured to secure his entry into the dyestuft 
created for the Royal Institution as a centre of scientific | industry ; had Dewar’s masterful energy been operative 
NO. 2788, VOL. 111] 
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