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of Edinburgh, Session 1873 - 74 . 
Thomson’s absence, owing to the inexperience of the young 
engineer to whom it was intrusted. Fortunately two other docks 
from Mr Thomson’s designs were in course of construction, — one 
for the French Government at Saigon, and the other for a com- 
pany at Callao. These have been thoroughly successful. 
In 1862 Mr Thomson retired from business in Java and settled 
in Edinburgh. lie devoted much time and labour to perfecting 
the elliptic rotary engine, a clear and simple model of which may 
be seen in the Industrial Museum. His next invention, the Road 
Steamer, was the result of a direct practical want. An efficient 
traction engine was required for the transport of sugar-canes in 
Java, and none could be found capable of doing the work. Mr 
Thomson recurred to his old idea of india-rubber tires, and found 
in these a solution of the main difficulty in designing a traction 
engine. The tires are not fastened to the wheel, but adhere to 
it by friction. They form a broad pad or elephant’s foot, by which 
the great weight of the engine is distributed over a large surface. 
The outer surface adapts itself to every peculiarity of the ground, 
and the inner surface forms, as it were, a constant endless platform 
on which the comparatively rigid engine works. The india-rubber 
does in a thoroughly practical manner what Boydell attempted to 
do by his impracticable endless railway. Both inventors wished 
to enable the steam-engine to work under constant conditions, but 
Mr Thomson’s plan is strong, simple, and yielding, where Boy- 
dell’s was weak, complex, and rigid. The perfect success of the 
plan is perhaps best attested by the numerous imitations which 
it has called forth, the object in most of these being to dispense 
with the expensive material india-rubber. The steel-protecting 
grooves for the tires are a later invention, and only a day or two 
before his death the inventor made an important improvement 
in their construction. 
The zeal and energy of the true inventor in conquering difficul- 
ties and discouragement have often been told. Those who had 
the privilege of knowing Mr Thomson have seen this spectacle 
heightened in tragic interest by the grandeur of mind with which 
he contended against the terrible malady which has so much too 
soon closed his labours. If mental and moral qualities could be 
as simply described as mere mechanical inventions, more should 
