Persons may be lowered by this rope, by fastening them at the end--as, for instance, by tying it under their arms, or placing them in a sack and fastening the rope to it--and then allowing the rope to gradually slip through the hands of the person lowering them. Better still, the rope should be bent round the corner of the window-sill, or round the corner of a bed-post, when the friction on the hands will not be so great, and the gradual descent will be safe-guarded. In descending alone, a person will find the knots of great assistance in preventing him from slipping down too fast; and he may increase the safety of his descent by placing his feet on the wall as he moves his grip, one hand after the other, on the rope; this arrangement prevents the friction on the hands, which hurried sliding might cause, with its attendant danger of falling. Permanent fire-escapes are provided in large buildings by means of iron ladders or staircases at the back or sides of the structure, with balconies at each story; while poles having baskets attached, ropes with weights so that they may be thrown into windows, and various contrivances and combinations of ladders, baskets, nets and ropes, etc., have all been recommended or brought into use during a long course of years. They are designed to afford escape, either from within, or from without, the burning building; several, however, being for private installation. [Illustration: STERN OF YARROW'S FIRE-LAUNCH.] Returning, then, to the public improvements in fire extinction, a new and remarkable floating fire-engine was designed about the year 1898, by Messrs. Yarrow & Co. of Poplar, in conjunction with Commander Wells, chief of the London Brigade. It was intended for use in very shallow water. The plan was cleverly based on the lines of the _Heron_ type of shallow-draught gunboats constructed for use on tropical rivers. Six of these vessels were built by Messrs. Yarrow for the Admiralty, and two went to the Niger and four to China. The new fire-float design provided for twin-screw propellers fitted in raised pipes, or inverted tunnels, to ensure very light draught combined with high speed, and the consequent power of manoeuvring quickly quite near to the shore. The difficulty of working fire-floats close to the shore in all states of the tide had long troubled the London Brigade, and rendered the best type of vessel for this purpose a matter of much concern. Originally, vessels of comparatively large size were used, containing machinery both for throwing water and for propelling the boat. These vessels, however, were costly to maintain, and could not be effectively used at all states of the tide. Captain Shaw, therefore, separated the fire-engine from the propelling power, using tug-boats which would float in a few feet of water to haul along fire-engine rafts, which could be used quite near to the scene of the fire.