‘216 THE STRUCTURE AND LIFE OF BIRDS cuHap. 
is often quite inaudible. Even when we can‘hear the 
note it does not tell us much. It depends on the 
‘rapidity with which the extremity of the wing moves, 
not on the number of wing-beats in a second, and so 
cannot tell us what we want. 
(3) We now come to the graphic method, in apply- 
ing which Professor Marey has shown wonderful skill. 
‘A sheet of paper blackened by the smoke of a candle 
was ‘stretched upori a cylinder, which was made to 
‘revolve at a uniform rate. An insect, the frequency 
‘of whose wing movements was to be’studied, was held 
-by the abdomen in a delicate’ pair of forceps, and was 
-placed so that one of its wings, at every up or down 
stroke, brushed against the blackened paper. With 
‘birds the method was, necessarily, far more elaborate. 
On the extremity of the wing an apparatus was placed 
which at each alternate movement broke or closed: an 
electric’ circuit. In Professor Matey’s book (Animal 
Mechanism, p. 230) the bird may-be seen-carrying his 
burden of electric wires and other machinery. As in 
the case of the insect, a’ tracing was made on a 
revolving cylinder. 
The results were: 
Revolutions of wing 
per second. 
Sparrow ‘an on i doe sel 
Wild Duck ... — - ih: aS) 
Pigeon... 9... Re make . 8 
Screech Owl ... atk ee ei oe 5 
Buzzard os ; 3 
‘These results seem quite dependable, and it is much 
to be regretted that we cannot arrive at conclusions 
