KNOWLEDGE A: SCIEXTIEIC NEWS. 



[JUNli, 1(,05. 



to be due to the restoration of energy from the forward 

 stressed feather. (The portion which the present 

 writer ventures to indicate between the lines k and k' 

 seems to be from just before the commencement of the 

 down stroke to the commencement of tne next.) 



The curve (Fig. B) was recently obtained by Major 



B. Baden-l'owell in the loilowing wav : -Small birds 

 were procured, and tubes of paper were prepared, 

 whose internal diameters were approximately the 

 distance between the tips of the outstretched wings of 

 these birds. The internal surfaces of the tubes were 

 covered with a coating of lampblack. A tube was 

 then arranged with one end in a room and the other 

 end pointing out of doors through an open window, 

 and a bird liberated within the inner end of the tube. 

 .\s it P.cw out towards the light a record of the move- 

 ments of the wing tips was obtained by the tips of the 

 feathers scratching off the lampblack. Several 



observations were made, a fresh tube being used each 

 time. On page 121 is a reproduction of one of the actual 

 records (reduced in size). 



Major Baden-l'owell considers these marks to repre- 

 sent the down stroke, and the light scratchings seem to 

 show that the wing is flexed on the up stroke. 



The writer ventures to think that the difference in 

 the distinctness between the two portions is due to the 

 wrist being in a slightly flexed condition on the up 

 stroke in what may be considered the normal position, 

 and that on the down stroke the stressing of the 

 primaries automatically increases the distance between 

 the wing tips and opens the wrist automatically against 

 its elastic re-action. The wing as a ivholc is essentially 

 an elastic structure. The absence of recurvation at 

 the lower portions of the record taken in conjunction 

 with the form of the down stroke record, would seem 

 to show that (being in the tube) the bird was not 

 flapping at full vigour, or quite normally, and that the 

 stored energy of the primaries was given out during 

 the latter part of the down stroke. 



During flapping flight the primary feathers auto- 

 matically exert a clawing swimming action. 



In reference to the Hargrave curve, Mr. Hargrave 

 has demonstrated that when air is blown against such 

 a curved surface — thus 



— a lift is obtained against the bight of the curve. He 

 arranged little trap-doors opening upwards, which 



liK. 1. 



