REACTIVE LOCOMOTION. 
35 
800 times lighter than water , and 6,400 times lighter than 
iron . Other things being equal, the refiftance of a fluid to 
the furface that oppofes it is proportioned to the relationftiip 
between the fpecific gravities of the two, for juft as many 
times heavier as is the oppoftng body or furface than the 
fluid to which it is oppofed, to this extent will it cut into 
inftead of being refifted by the fluid. I am aware that it 
may be replied to this, that when air is driven at the high 
velocity employed in fan-blowers the fluid becomes practi¬ 
cally so denfe as to admit of being dealt with the fame as 
water. Very true as far as it goes. But why ufe up the 
power required to bring it to this denflty ? Why not em¬ 
ploy lefs power, and deal with the fluid as it is naturally ? 
This is what the dragon-fly and infeCts typified by the 
dragon-fly do. 
The wings of infeCts are perfedt goflamer, ftronger and 
finer than the fineft and lighted: of fabrics that man can 
weave or make. From under the horny coat of mail which 
the beetle opens, fee what a marvelloufly tranfparent tiflue 
is unfolded to the breeze. From its crumpled condition 
one wouldn’t imagine it wings. And the wings of the 
birds, what miracles of ftrength and lightnefs! But why 
the body heavy and wings light ? The body is to cleave 
the air, the wings to oppofe it. 
But man makes the wings of his fan-blower of metal — 
thin metal, it is true, but metal, neverthelefs—in fpecific 
gravity 6,400 times heavier than air! The contrivance is 
