28 
the action of this principle alone, (and such a thing is possible) the 
most suitably organized animal for swift motion on the wing would 
never attain a degree of velocity above fifty miles per hour in a still 
atmosphere. And therefore, I conclude that graritation and acceler- 
ation, acting in combination, produce the usual horizontal motion of 
birds of passage, of about one hundred miles per hour. 
Entered according to act of Congress in ihe District Court of the United Slates for the Dis- 
trict of Columbia, by R. O. Davilsox, the nineteenth day of May, 
one thousand eight hundred and fifty -eight. 
