MOVEMENTS OF THE WINGS OF BIRDS. 251 



scrawl. It is indispensably necessary so to arrange the 

 instrument that the points of the levers should touch the 

 cylinder only at the moment when we wish to register the 

 phenomena, and to cease this contact after one, or at most 

 two revolutions of the cylinder, in order to avoid confusion in 

 the tracings. 



We have recourse, for this purpose, to the arrangements 

 already made in our experiments upon walking. 



Fig. 103 shows the experimenter mt the instant when he 

 is about to take a tracing from the pigeon. Observing the 

 flight of the bird, he seizes the moment when it becomes 

 regular, and squeezes the india-rubber ball. The contact of 

 the levers is immediately produced, and the tracing is made. 

 After a second and a half he ceases to press it, the spring 

 removes the levers from the cylinder, and the tracing is over. 



With a little practice it is very easy to ascertain the dura- 

 tion of the revolution of the cylinder, and to confine the 

 tracing to the necessary length. 



This long description was necessary, as we were anxious 

 to make this apparatus understood, it being the most im- 

 portant of all, on account of its double function. We shall 

 have to employ it, not only in the analytical, but also in the 

 synthetical part of these studies, when we shall attempt to 

 represent the movements in the bird^s flight. 



New determination of the trajectory of a hircfs wing. — A 

 pigeon was made use of in this experiment. It was a male 

 bird of the variety called the Roman pigeon, very vigorous, 

 and accustomed to fly.^' Fig. 104 shows the arrangement of 

 the apparatus which we have used for the purpose of study- 

 ing its movements. 



It is more especially to the humerus that we have directed 

 our attention, in order to obtain the movements of the wing in 

 space. For this purpose a wire is twisted round the bone, 

 holding it as in a ring, and furnishing by its free ends a firm 

 point of attachment outside the wing for other wires which 

 act on the experimental drums. 



* This latter point is of great importance, for the greater part of the 

 birds in a dove-cot are of no use to us, on account of their inexperience in 

 flight. 



