Naval experts do not always agree as to the differences between a battleship and a cruiser. There are vessels in either category which could not possibly be placed in the other; but on the other hand there are some vessels that may be classed as either one or the other, and the types of the fast battleship and the armoured cruiser have been approaching each other in late years in so many respects, that some cruisers are fit to take their place in the line of battle against all but the heaviest battleships, and the natural result has been the appearance of the latest type of warship suitable for either duty, and known as the cruiser-battleship. [Illustration: THE GERMAN DREADNOUGHT CRUISER “VON DER TANN.” _Photograph by Stephen Cribb, Southsea._] The Japanese, in their encounter with the Russian fleet, utilised cruisers against the Russian ships of the line, but whether they would have been able to do so had the Russian battleships been in as good condition as were those of their Oriental opponents is a point upon which opinions differ. The cruisers, like the latest _Invincibles_, have been given the armament of a battleship, but they have been less heavily protected in order to allow them superior speed; everything, should they have to take part in a naval battle, will therefore depend upon their antagonists and the exigencies of the engagement as to the duties they will have to perform. Every nation has its own classification of warships, and the varieties of modern warships are so numerous, and the estimates of their effectiveness so much at variance, that it is little wonder the descriptions assigned to the vessels do not agree. Thus the American _Maine_, sunk at Havana, was described with equal accuracy as a cruiser and as a second-class battleship. But the nations have, for the most part, adopted the British classification of cruisers, though they have not failed to modify it to suit their own views. First come the unprotected cruisers, then the protected cruisers of the first, second, or third class; then the armoured cruisers; and of recent years the battle-cruiser, or heavy cruiser, capable of taking her place in the line with battleships. The unprotected cruisers have no side armour or other protection worth mentioning, and are mostly used for police duties, such as guarding fisheries, etc. They are lightly built and armed, and of relatively good speed for their size, and the duties they have to perform usually constitute the chief matter for consideration in the design of the several vessels. The protected cruisers have strong steel decks to protect their engines, etc., besides a great number of watertight compartments, and are classified according to their size, armament and speed, and the work for which they are intended.