FLIGHT OF INSECTS. 



I'.ll 



is adapted to other experiments iutended to verify those which 

 Me have already made l<y other means. By van ing- the inci- 

 dence of the wing on the revolving cylinder, \ve cau foretell 

 what will be the figure traced, if it be true lhat the 



win; 



r. ally d* scribes \hi i'oriu of au 8. Thus, if we obtaiu a figure 



Kio. To. Tracings of the wing of a wa<*p ; several of the lowi-r In V s r "'" 1 

 dist.n -tly sjen Tliis traci'iir was nbtiiue'i by I'oldintr the insect sins 

 to rub the cylinder by the hinder puint oi the wing, which gives very ex- 

 ten' led curves 



conformable to that which we have foreseen, it will be an 

 evident proof of the reality of these movements. 



Fin. 7<t. Tracing of a Wheattone's kaleidophone rod, timed to the octave, 

 that is to say. vihr itinsf twice transversely for each longitudinal vibration. 

 (This figure is ta vCn from 14. Kceniar. ' The slackeirni,' speed of the 

 cylinder producer an app;oxima ion of the cui ves towards, the end ot the 

 figure. 



Let us suppose that the wing of the insect, instead of 

 touching the cylinder with its point, as we have seen just 

 now, brushes it with one of its edges ; and let us admit for 

 an instant that the 8 described by the wing is so lengthened 

 that it departs but slightly from the plane passing through 

 the vertical axis of this figure. If we press the wing slightly 

 against the cylinder the contact will be continuous, mid the 

 tracing uninterrupted ; but the figure obtained will no 

 longer be an 8 , if the cjiinder be immovable it will be an 

 arc of a circle, whose concavity will be turned towards the 

 point of insertion of the wing, a point which will occupy pre- 

 cisely the centre of the curve described. 



