July 11, 1884.] 



KNOWLEDGE 



25 



and thorax and long, tapering body, and tbey swim about 

 head downwards. Near the tail, a straight bianch, carry- 

 ing a number ot hairs at its tip, pi-qjccts at an angle with 

 the body. This is a respiratory tube, and communicates 

 both with the outer air at its tip, and with the tracheal 

 system at its base. All that is necessary for breathing, 

 therefore, is that the tip of this tube should be above the 

 surface. Accordingly, when at rest, the larva takes up 

 this position, while at other times it goes wriggling about 

 through the water, being of sufficient buoyancy to rise 

 without ettbrt to the surface when occasion demands. After 

 several changes of skin the pupal stage is reached, and the 

 last moult is accompanied by a remarkable alteration in the 

 appearance of the insect. The head and thorax now appear 

 as if thrown into one large mass, from which the body 

 tapers away. But the most astonishing change of all is 

 that which takes place in the respiratory system ; the 

 entrance to this is now transfeiTed to the opposite end of 

 the body, and appears as two small twisted horns projecting 

 from the gigantic head. If now the insect were to retain 

 its inverted position, there would obviously be no possibility 

 of bringing these breathing horns nearer the air than a 

 whole body's length ; therefore, it turns a somersault in 

 the water, and henceforth goes about head uppermost, an 

 attitude which, when it is at the surface, brings the organs 

 in question just above the water. Though the creature is 

 now a pupa, and can take no nourishment, it is possessed of 

 almost as much freedom of motion as before, and jerks 

 itself about by vigorous wrigglings of its awkward form. 



(To he continued.) 



A NOVEL FIRE-ESCAPE. 



THE sides of the block are united by four friction pins, 

 arranged on two diagonal lines, and over which the 

 rope or wire is passed (as clearly shown in the engi-aving). 



of the block runs a traveller, to which one end of a belt of 

 leather or webbing is secured, the other end of the belt 

 being provided with a hook to be passed over the rod. 



To use the e.'^cape, one end of the rope is hooked in the 

 window-sill, and the other end thrown out of the window. 

 The belt is passed round the body, and the hook clasped 

 over the side rod. Then the person steps out ot the window 

 and slides slowly down the rope, the friction pins in the 

 block preventing a rapid descent. By means of the brake 

 levers the appaiatus can be stopped at any time. When 

 the block arrives at the ground, the person unfastens the 

 belt, and the block is pulled up again to be used by 

 another person, who throws the end of the rope that had 

 been fastened in the room out of the window, and secures 

 the opposite end. The device is portable, takes up a small 

 space in a gripsack, and weighs but little. 



This invention has been patented by Messrs. David 

 ^Yare and C. W. Richman, of Philadelphia, Pa. — Hcientijir 

 American. 



The rope is also passed over pins at the top and bottom of 

 the block. At each end of the block is pivoted a brake 

 lever, the inner ends of which press the rope against the 

 pins. On a rod secured to one of the outer side surfaces 



NOTES ON FLYING AND FLYING- 

 MACHINES. 



By Rich.*rd a. Proctor. 



(Contimied from page 4.) 



BUT although the reasoning of Borelli suffices perfectly 

 well to show that man can never fly by attaching 

 pinions to his arms, and flapping these in imitation (how- 

 ever close) of a bird's action in flying, it by no means 

 follows that man must be unable to fly when the most 

 powerful muscles of his body are called into action to move 

 suitably-devised pinions. M. Besnier made a step in this 

 direction (towards the close of the last century) when he 

 employed, in his attemjits to fly, those powerful muscles of 

 the arm which are used in supporting a weight over the 

 shoulder (as when a bricklayer carries a hod, or when a 

 countryman carries a load of hay with a pitchfork). But 

 the way in which he employed the muscles of the leg was 

 less satisfactory. In his method, a long rod passed over 

 each shoulder, folding pinions being attached to both ends 

 of each rod. When either end of a rod was drawn down, 

 the descending pinion opened, the ascending pinion at the 

 other end clo.sing ; and the two rods were worked by alter- 

 nate downwaid pulls with the arms and legs. The down- 

 ward pull with the arms was exceedingly etiective ; but 

 the downward pull with the legs was altogether feeble. 

 For the body lying horizontally, the muscles used in the 

 downward pull with the legs were those by which the 

 leg is carried forward in walking, and these muscles have 

 very little strength, as any one will see who, standing 

 upright on one leg, tries, without bending the knee of the 

 other, to push forward any considerable weight with the 

 front of this leg. 



Yet even with this imperfect contrivance Besnier achieved 

 a partial success. His pinions did not, indeed, serve to raise 

 him ii) the air ; but when, by a sharp run forward, he had 

 brought that aerial supporting power into action of which 

 we have spoken above, the pinions, sharply worked, so far 

 sustained him as to allow him to cross a river of con- 

 siderable width. It is not unlikely that, bad Besnier pro- 

 vided fixed sustaining surfaces, in addition to the movable 

 pinions, he might have increased the distance he could 

 traverse. But, as regards flight, there was a further and 

 much more serious defect in his apparatus. No means 

 whatever were provided for propulsion. The wings tended 

 to raise the body (this tendency only availing, however, to 

 sustain it) : but they could give no forward motion. With 



