In aid of stationary engines, "surface evaporator condensers"
have been found very useful, particularly where the supply of water is
very limited; and at waterworks it is now very common to pass the whole
water pumped through a surface condenser, thus giving a good vacuum
without the expenditure of any water, and with the result of only
raising the temperature of the water a very few degrees, on account of
its large volume.
Locomotives have shared to some extent in the general improvement in
machinery. The boilers are better made, and are safer at the higher
pressures now carried than they were formerly with a low pressure.
Several new valve gears of great promise have been brought forward, both
for locomotives and marine engines. Among them Joy's motion should be
again noticed. Mr. Webb says: "The engine shown at Barrow has been at
continuous work ever since the Barrow meeting, and has run 30,278 miles;
we had it in for examination on the 18th inst., and found the motion
practically as good as the day it went out of the shop, more especially
the slides, about which so many of the people who spoke at the meeting
seemed to have doubts. I do not think you could get a visiting card
between the slides and the blocks; in fact, the engine has been sent out
to work again, having had nothing whatever done to it.
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