Primary Feathers in Flight. 



155 



ilar curves have been obtained by artificially interlocking the 

 primaries for several hours and then measuring the recovery 

 of the web of the feathers with a micrometer microscope. It 



Fig. 9. Notch in the first primary feather of a Sharp-shinned hawk 

 formed by the interlocking of the feathers. Photograph taken 18 minutes 

 after the bird was killed. (Round object is a large thumb tack holding 

 feathers in place.) 



10 



:. 



Fig. 10. Notch in the first primary feather of an Osprey formed by the 

 interlocking of the feathers. Photograph taken 60 minutes after bird was 

 killed. 



was found that artificial interlocking of the feathers for fifteen 

 minutes produced either no notches or those that were small 

 and rapidly disappearing, while interlocking them for several 



