Besides growing downwards the idea also grew upwards, and resulted in the building of six ships of the “Admiral” class, of which the first was the _Collingwood_. These, which were the apotheosis of the Barnaby idea, represented an absolute revolution in naval construction, so far as big ships were concerned. The “Admirals” were not all identical, as they formed four different groups in the matter of displacement and three in armament. In all, however, the integral idea was the same. Amidships was a narrow belt, 150ft. long by 7½ft. wide, which sufficed to protect engines, boilers, and communication tubes of the barbettes. This belt varied in thickness from 18ins. to 8ins, of compound armour. The ends of the belt were closed up by 16-inch bulkheads. Forward and aft was merely a curved protective deck; there was also a flat protective deck on top of the armour belt. The ships were of low freeboard, forward and aft, but had a large superstructure built up amidships. At either end of the superstructure, with their bases unprotected by armour except for the communication tubes already referred to, were many-sided barbettes with plates set at an angle of about forty-five degrees. These barbettes were about 11½ins. thick, and carried each a couple of the heaviest guns then available. These were 12-inch breechloaders in the _Collingwood_, and 13.5-inch in the other ships, except the _Benbow_, which mounted one 16.5 inch 110-ton in each barbette instead. An auxiliary armament was mounted inside the superstructure. The speed of these ships was about seventeen knots, and was considerably in excess of the average for the period.