These vessels are 10 feet 6 inches beam; draught of water about 5 feet. They are built of heavier plating than the _Lightning_, and are guaranteed to maintain a speed of 18 knots. The propellers in these boats are placed in front of the rudder, so as to give increased readiness in steering. In order to prevent oxidation as far as possible, the plates and frames below the water line are galvanised. A spark-catching apparatus is fitted to the base of the funnel, so as to prevent the position of the boat being betrayed to the enemy at night. The armament of these vessels consist of an outrigger arrangement similar to that described at page 167. They are also well adapted for the Whitehead torpedo. They are also provided with a strong buffer in the bows for deadening the shock, in the event of their coming into contact with an enemy's vessel at too high a rate of speed. _"Second Class" Boats and Mode of Manipulating the Fish Torpedoes from them._--Another type of Thornycroft torpedo boats, several of which have been built for continental governments, and which is termed "Second class," is shown at Fig. 155. These boats are 60 feet long, 7 feet 6 inches beam, and draw some 3 feet of water; their guaranteed speed being 16 knots per hour. The mode of carrying the Whitehead fish torpedo, and manipulating it from such a boat by means of Mr. J. I. Thornycroft's invention, which has been fully described at page 140, is shown at Figs. 155 and 156, where Fig. 155 represents both torpedoes housed, and Fig. 156 one torpedo in the firing position, the other one being housed. Four of this type of Thornycroft torpedo boats were attached to H.M.S. _Hecla_ during her recent cruise in the Mediterranean, and have been very favourably reported on as follows:--They do not suffer from the blows of the sea, nor from the strains incident upon hoisting in and out; nor yet when they are suspended ready for lowering, in which latter position they have frequently remained for twenty-four hours; that under careful management they are perfectly safe in a heavy sea, and they possess good manoeuvring powers. The Thornycroft torpedo frames were found to perform well the services for which they are intended. When proceeding at ordinary speed they are nearly noiseless, and cannot be seen on a dark night at a distance of 100 yards. _The Thornycroft Propeller._--All the torpedo boats built by this firm are fitted with the propeller invented by Mr. Thornycroft, and which bears his name. It is a modification of what is known as the Dundonald propeller, the principal difference being that in the Dundonald propeller the blades are inclined backward in straight lines, while in the Thornycroft propeller they are curved.