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FIRST PRINCIPLES OF AERIAL TRANSIT. 
By F. H. WENHAM, C.E. 
NIMPEDED by all terrestrial obstacles — to man impassable 
without the aid of science — birds of passage traverse with 
ease their aerial roadway with level track, making every chosen 
spot of earth alike their home, instinctively directed by change 
of season to more congenial climates. 
The question is frequently asked, Is man ever destined to 
accomplish this sublime mode of locomotion, or is it always to 
remain the sole privilege of unthinking animal creation ? The 
answer is generally in the term “ impossible,” so far that it is a 
common proverb uttered to express the height of impossibility. 
It is not an easy task for objectors to explain the conditions 
on which such a very positive assertion is based. It is generally 
summed up in the statement, “ Not power enough ; the pec- 
toral muscles of birds are enormously strong in proportion to 
their weight, far exceeding those of any terrestrial animal.” 
And thus the argument is abruptly dismissed. But this reason- 
ing is both unphilosophic and untrustworthy, and forms no 
criterion for the determination of a mechanical condition of 
actual work performed ; for a large bird must of necessity have 
powerful pectoral muscles, merely for the purpose of sustaining 
the weight of the body on those wings, even supposing that 
they rested on solid supports or props. The wings are hinged 
to the body like levers, and these huge muscles are needful 
merely to supply the place of rigidity when no mechanical 
force is expended in the way of motion. Rejecting, therefore, 
the size of muscles as an uncertain proof of acting force, as far 
as it relates to rapid motion, and avoiding all abstruse calcula- 
tions and complex formulae, let us consider a few of the acting' 
laws involved in the question of flight. 
There is no principle in mere rapid horizontal movement 
alone that would cause a heavy body to maintain its level, for 
during this motion it is still answerable to the laws of gravity. 
If a leaden ball is set free in vacuo, it will fall sixteen feet in 
the first second of time. If that same ball is fired horizontally 
