RECORDS 57 



of hawks, eagles and certain other birds are interlocked in 

 flight. The speaker referred to his original paper on the subject 

 in which the theory was set forth, which was presented by the 

 late Professor W. P. Trowbridge before the National Academy 

 of Sciences and the New York Academy of Sciences. The 

 paper created some discussion in Science at the time, partici- 

 pated in by Dr. Elliot Coues, Professor Newberry, Professor 

 Trowbridge and others. Mr. Trowbridge showed by a number 

 of diagrams and photographs that the primary feathers of a 

 number of birds are emarginate near their ends, and that the 

 webs of the feathers are so shaped that when they are over- 

 lapped, a curved and rigid aeroplane is formed at the end of the 

 wing, which, he considered, is of considerable advantage -in 

 swift sailing flight. The emarginations of the primaries of 

 hawks and eagles are particularly pronounced, and permit firm 

 interlocking. A table of observations was given, showing that 

 the interlocking of the primaries does take place, the data hav- 

 ing been obtained at New Haven during the autumn flights of 

 hawks along the Connecticut coast. It appears that in the case 

 of one species of hawk examined, ten wings out of forty had 

 all five primaries interlocked, and that the number of wings 

 having 60 per cent, of the primaries interlocked was twenty- 

 nine, or 72 per cent, of the total number, forty. It was concluded 

 that emarginate primaries of hawks and other birds are inter- 

 locked in flight on the following grounds : (i) It has been found 

 that the webs of such feathers of hawks that had just been 

 killed usually show deep notches where they have rested against 

 one another, which notches could only result from habitual 

 interlocking of the primaries ; and (2) in every case of over 

 twenty-five hawks killed while flying and examined immediately 

 after they fall so}ne primaries were interlocked (several slightly 

 wounded birds not included). In the case of nineteen perfect 

 specimens on one species, 67.9 per cent, of all emarginate pri- 

 maries (190) were found to be interlocked. While it is not pos- 

 sible at present to show when the emarginate primaries are 

 interlocked in flight the indications are, however, that this occurs 

 when the wing is partly flexed, as in the case of hawks sailing 



