NEW RESULTS IN ANIMAL MOVEMENTS. 



453 



T 4 o of a metre in circumference ; one-half of its circumference is cov- 

 ered with a metallic band, the other half is formed of insulating mate- 

 rial. Metallic springs press against the periphery of the pulley, so that, 

 while they touch the metallic band, a current from a battery depresses 

 the lever which traces on the revolving cylinder. Hence the lever is 

 depressed, while T 2 of a metre of the cord pass, and it is elevated 

 during the next T 3 7 of a metre of passage of the cord. Thus are regis- 

 tered, in an indented line, the velocities of translation of the artificial 

 bird. Evidently the greater the velocity of the bird the greater will 

 be the number of indentations inscribed in a second on the uniformly- 

 revolving cylinder. 



~U"UTJ1JTJ1JXJT_JTJ1J 



ONE SECOND 



Fig. 4. 



2. Measurement of the Duration of the Depression of the Wings 

 A second electrical recorder, similar to that which registers the turns 

 of the pulley, serves to determine the duration of the depression of the 

 wings. For this purpose it is necessary that, at the beginning of the 

 depression, the current of a battery should be broken, and this action is 

 registered on the revolving cylinder by an indentation in the trace of 

 the writing-lever ; also, at the end of the depression of the wings, the 

 current must be closed again, and this instant is likewise registered 

 on the cylinder. 



