2GS 



ANIMAL MECHANISM. 



second question \\liich we have to solve relates to the deter- 

 iniiiutiun of the various phases in the rapidity of flight. It 

 niav receive, its isulutii)ii by the employment of the same. 

 method. If the drum, loaded with a piece of lead, be placed 

 ou the back of the bird so as to present its membrane, in a 

 vertical plane that is, at right angles to the direction of flight, 



ii: 114. Iu the upper part we sec. ]>l:n'. <l :i)>. .vr mcli oilier, the muscular 



t'.-u-in^ (see )> j::2i. ami that of ihu vertiral i>si-ill;ilimis in a wil<l duck. 

 I 'in Iff tin 1 iiiiilulatimi ", whirli slinw.s tin- cli 'V.i tii in uf thu win^'. is MM'II :i 

 M'ftii-al i>M'illati 'ii ; ani.tlirf is M'L-M iin.lrr/i. thu tr:iriiiK ci >n < s|KHiilin^ 

 witli tin' ili-pu -sii.ii ..I tin' win^'. In the lower hall' of tin figure arc 

 t - ii in:' s rolli rtc'l fri.i 1 1 a In I //aril ; tin' o.-r illation at ". wliirli rorrr.s|ii nius 

 with thu cluvatii'ii ot tin uin^, is IL-KS marked than that from the duck. 



the apparatus would be insensible to vertical oscillations, and 

 \\onld only give the signal of those which are made backwards 

 and forwards. Let us turn the membrane of the drum in 

 iron) ; it. is evident that if the bird quickens its speed, the 

 retarding- influence of the inertia of the mass of lead \\ill 

 produce a pressure 071 the membrane of the drum ; (lie air 

 will be compressed, and the registering lever will rise; while 



