course, priming must be carefully guarded against. Of course, the salt
water distilled will affect the working, not exactly of the distillers,
but of the boilers. If the water in the harbor, as is not improbable, is
muddy, some method of filtering it before pumping it into the boilers
ought, if at all practicable, to be resorted to, for the twofold reason
of preserving the boiler plates from muddy deposit, and also to prevent
priming, which would certainly ensue from the use of muddy water. No
doubt the medical staff take care that the distilled water is alike
thoroughly aerated and efficiently filtered. The most successful method
of aerating is, we believe, to cause the current of steam as it enters
the condenser to suck in air by induced current along with it. The
filtering ought not to present any difficulty, as at all events sand
enough can be had. Charcoal, however, is another affair, and all
distilled water ought to be brought into contact with this substance.

Simple, however, as such an arrangement as this appears to be, practical
difficulties, which it is _said_ are insurmountable, stand in the way of
its adoption, and the distilled water produced for Egypt is made in
special apparatus, and various forms of condenser are employed, made
under various patents. The principle involved is, however, in all cases
the same. Steam is generated in one of the ships' boilers, and condensed,
filtered, and aerated in a special apparatus. The great objection to the
use of the ordinary surface condenser is that the main engines would, in
the majority of cases, have to be kept going, in order to pump the
distilled water out of the condenser, and to supply circulating water.
But it is easy to see that if engineers thought proper, this difficulty
could be readily got over. Separate circulating pumps, usually
centrifugal, are now freely used, and the addition of a special pump for
lifting the condensed water presents no difficulty whatever. While the
main engines are running, the withdrawal of much condensed water would