The next step in reducing armament and increasing speed, produced the protected cruiser, which carries no armour belt, but retains the protective deck, upon the sloping sides of which is stored the coal. The turrets disappear altogether, and there is usually only one 8-inch gun, the battery being principally made up of 4-inch rapid-fire guns and 6, 4, and 1-pounders. As this class of vessel is not able to cope with the armoured cruiser, it must be faster, for the general principle holds good that the weaker the vessel becomes in point of offensive weapons or defensive armour, the greater the necessity that she should be able to run away. The best types of the protected cruiser in the navy may be found in the _Columbia_ and _Minneapolis_, which have a speed of about twenty-seven miles an hour. The weakest class of all is composed of the unprotected cruisers, which have neither armour-belt nor protective deck, and carry only light batteries of rapid-fire guns. When these vessels are slow, like the _Detroit_, they are intended for long voyages and for duty in foreign countries, and are of little use in a sea fight. The very fast unprotected cruiser, like the American line steamers, _St. Paul_ and _St. Louis_, attach little importance to their armament, and rely for protection upon stowing the coal behind the place occupied by the armour belt in other vessels. All the beautiful wood-work, which was so much admired in these vessels, was ripped out to make room for these coal-bunkers, which are sufficient to protect them from anything but the heaviest guns. On account of their extreme weakness as fighters, these cruisers are necessarily the fastest of all the large vessels, and can run away from anything. For this reason no concern was felt for the _Paris_ by those who knew the principles which govern the safety of modern vessels. The various types of cruisers are not expected to fight with any but vessels of their own class, which they may encounter in the discharge of similar duties, such as scouring the seas as the advance guard of the slower line of battle-ships, preying upon or escorting merchant vessels, blockading ports, and acting as convoys for troop-ships. Gunboats are simply light-draught cruisers, and are intended for use in shallow waters and rivers.