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Reviews.



to accomplish their aerial evolutions. In the work before us,

Mr. Headley has attempted, and very successfully, to supply this

deficiency, and throughout the book he has avoided as far as

possible the deep mathematical and dynamic problems which

underlie the subject, and has expressed in clear and straight¬

forward language the methods by which flight is accomplished.


The bird, as he points out, must be considered as a highly

efficient aeroplane, and the difficulties which Nature has had to

overcome are precisely those which are at the present day con¬

fronting the human aviator. By a careful study, therefore, of a

bird’s methods and structure the airman can most surely discover

the problems that he himself has to face, though in all, save the

essentials he will have to overcome them by different methods.

Mr. Headley has borne this fact in mind and has arranged his

book accordingly; the first three Chapters deal with Gliding,

Stability and Motive Power, after which follow chapters on

Starting, Steering and Stopping. The latter half of the book

treats of the subject rather from the bird than the airman’s stand¬

point, and we have notes on the Structure of Birds, Varieties of

Wing, Rate and Duration of Flight, and finally the very important

effect of Wind and the various ways by which it is turned to

account. In a book so excellent of its kind there is but little

to find fault with, and our criticisms, such as they are, are mostly

matters of opinion. We cannot for instance agree with the

author when he claims that the relative shortness of leg among

the larger birds has probably been a factor in keeping birds, as

compared with mammals, comparatively small. The Flamingo,

a typical long-legged bird, rises from the ground with difficulty,

while several non-fliers have long legs. Our idea roughly has

always been that the power (muscles) required to raise a large

bird must of necessity be so large (i.e. heavy) that a limit of size

is soon reached, and to our mind a proof of this lies in the fact

that the largest birds, e.g. Ostriches, Rheas, etc. are flightless.

Helmholtz formulated this idea, and Mr. Headley, without in

our opinion sufficient reason, rejects it. With regard to the

Velocity of Flight, Mr. Headley is cautious, and at the most

allows an imaided flight (i.e. unaided by wind) of about 50-60

miles per hour, though he gives the record of a Swallow that



