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A PREFACE AND AN APOLOGY. 13 
the time, and could fee no meaning in the pertinacity 
with which the dragon-fly purfued me, I think I fee it 
now. 
Until the dragon-fly made its appearance, my thoughts 
on flying were running in the old grooves in which the 
thoughts of all men had been running for centuries, and 
running with utterly barren refults, viz., “ beating the 
air as birds wings do ! ” failing on <c inclined planes,” 
&c. See. 
And now comes along a creature viflting me fo con- 
ftantly, and in fo many wide-apart places, as to compel 
me to think of infeSls , and give them attention; fo that 
finally, after long years have pafled, I get to underhand 
that behind the dragon-fly is to be found the great law of 
Vacuum or Force-flotation, the condition precedent to 
all navigation of the air ! 
But although I felt greatly difappointed at the time 
with the refults of my experiments with the dragon-fly 
in the bell-glafs, I did not at once abandon my purfuit of 
the ideal fecret. I continued to watch the birds, and 
fometimes infedts, and record my “ thoughts on flying” as 
regularly as ever; and by-and-by I got hold of a little 
thread, that became to me finally the fcarlet clew out of 
the labyrinth I was in; and to teft the corredtnefs of my 
thought at the time, I made an experiment with an infeSl 
(the miller or moth fpoken of in the treatife following). 
After this I made four large wings in perfedt imitation of 
