is used so widely, very few accidents have occurred; and
in steam vessels the only additional source of danger is the salting of the
boiler. This may be prevented either by the use of fresh water in the
boiler, or by practising a larger amount of blowing off, to insure which it
should be impossible to diminish the amount of water sent into the boiler
by the feed pump, and the excess should be discharged overboard through a
valve near the water level of the boiler, which valve is governed by a
float that will rise or fall with the fluctuating level of the water. If
the float be a copper ball, a little water should be introduced into it
before it is soldered or brazed up, which will insure an equality of
pressure within and without the ball, and a leakage of water into it will
then be less likely to take place. A stone float, however, is cheaper, and
if properly balanced will be equally effective. All steam vessels should
have a large excess of boiling feed water constantly flowing into the
boiler, and a large quantity of water constantly blowing off through the
surface valves, which being governed by floats will open and let the
superfluous water escape whenever the water level rises too high. In this
way the boiler will be kept from salting, and priming will be much less
likely to occur. The great problem of steam navigation is the economy of
fuel, since the quantity of fuel consumed by a vessel will very much
determine whether she is profitable or otherwise. Notwithstanding the
momentous nature of this condition, however, the consumption of fuel in
steam vessels is a point to which very little attention has been paid, and
no efficient means have yet been adopted in steam vessels to insure that
measure of economy which is known to be attainable, and which has been
attained already in other departments of engineering in which the benefits
of such economy are of less weighty import. It needs nothing more than the
establishment of an efficient system of registration in steam vessels, to
insure a large and rapid economy in the consumption of fuel, as this
quality would then become the test of an engineer's proficiency, and would
determine the measure of his fame. In the case of the Cornish engines, a
saving of more than half the fuel was speedily effected by the introduction
of the simple expedient of registration. In agricultural engines a like
economy has speedily followed from a like arrangement; yet in both of these
cases