Page:Aerial Flight - Volume 1 - Aerodynamics - Frederick Lanchester - 1906.djvu/441

Rh In this instance the species of bird was not identified. This proportion means that the reaction sustained by the wings when in action is approximately four times the weight of the bird, on which computation the flight velocity should be about twice that proper to the actual weight and wing area measurement.

It is difficult to assess accurately the speed of flight of a bird under any circumstances, and most of all under the conditions now under discussion. Travelling at somewhat over thirty miles



per hour on a motor vehicle, it is not an uncommon sight to see a pied wagtail or other small bird endeavouring to escape directly ahead by adopting the mode of flight under discussion. When hard pressed in this way the wagtail flies low, and its motion closely resembles the bouncing of an india-rubber ball on the