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 emulation of foreign powers, but at that time they had neither engineers nor shipwrights who could pretend to rival ours.

It has been thought desirable to dwell at some length on the 'Iris' and 'Mercury,' because they undoubtedly indicate an epoch in the history of engineering in the navy and are still very valuable vessels. They have, however, two grave defects, which have prevented any reproduction of their type. They are entirely unprotected, and their coal endurance is very small. More or less provision was made in them to compensate for the absence of armour by water-tight subdivision and by coal protection; still they had to run the risk of being penetrated in a vital part and sent to the bottom by the explosion of a single successful shell.

And here came in one of the most important inventions, suggestions — call it what you will — of the quarter century we are discussing. That was the adoption in otherwise light cruisers of a steel protective deck, which has permitted the grand and beneficial substitution of vertical engines for horizontal ones. And for this idea Rear-Admiral Robert Scott deserves all the credit. The part of a fighting ship that it is most essential to guard from an enemy’s fire is the engine-room. In the early days of steam this was naturally accomplished by keeping all the machinery below the water line, but when the idea of a horizontal armoured deck took root engineers were quick to see that they would be comparatively safe under its shelter, and that projectiles would glance off it instead of dropping through to their destruction.