230 
THE BEAUTIFUL LADDER. 
like sound which has secured to the bird its 
common designation. 
“ The noble reasoner continues: ^ So many 
are these contrivances, so various, so fine, so 
intricate, that a volume might be written with¬ 
out exhausting the beauty of the method in 
which this one mechanical problem has been 
solved. It is by knowledge of unchanging 
laws that these victories over them seem to 
be achieved; yet not by knowledge only, ex¬ 
cept as the guide of Power. For here, as every¬ 
where else in Nature, we see the same myste¬ 
rious need of conforming to imperative condi¬ 
tions, side by side with absolute control over 
the forces through which this conformity is 
secured. When any given purpose cannot be 
attained without the violation of some law, 
unless by some new power and some new ma¬ 
chinery, the requisite power and mechanism are 
evolved generally out of old materials and by 
modifications of pre-existing forms. There can 
be no better example of this than a wing-feather. 
It is a production wholly unlike any other ani¬ 
mal growth — an implement specially formed 
to combine strength with lightness, elasticity, 
and imperviousness to the air. 
