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POPULAR SCIENCE REVIEW. 
the angle of inclination which the car would assume relative to 
the balloon, the car in this case being in advance. Of course a 
more suitable shape of the balloon would modify these condi- 
tions, but only to produce other elements of difficulty which 
cannot be overcome. For instance, as we depart from the 
spherical shape of the gas-holder the buoyancy decreases and 
its weight increases ! And particularly if some elongated form 
be constructed with conical or cigar-shaped ends, then struts 
must be employed to preserve its shape, and the extra weight 
to be thus sustained requires a balloon of such gigantic dimen- 
sions that, merely to inflate it, involves a cost quite out of pro- 
portion to any attainable result. No conditions except the 
exigencies of warfare would warrant the necessary expendi- 
ture. If any such conditions should ever attach to us as a 
nation, doubtless English talent will be equal to the emergency. 
Also if it be found desirable to escape from any besieged place, 
there will always be found sufficient of English body-linen, 
both male and female, for the whole population to float away, 
though perhaps in a makeshift manner. 
The apparent anomaly before alluded to, of the lighter 
element and the heavy bird — the denser element and, by com- 
parison, the light fish — is capable, however, of explanation, and 
its consideration will assist us in determining the conclusions 
at which the Aeronautical Society has arrived, viz. that flight 
is purely a mechanical action capable of imitation ; that it is 
unassisted by air-cells or other contrivances for effecting levity, 
and that the balloon is incapable of being rendered useful to 
man as a means of locomotion, except in the way of waftage, 
and that this mode of progression in relation to the earth is 
capable of being materially assisted by some method of raising 
or lowering the balloon at pleasure, without loss of gas or 
ballast. 
Let us suppose that the fish bears the same proportion of 
weight to its elemental medium as does the bird to the air. 
Judging from the fact that birds have been observed when shot 
to sink half their bulk in water, they may be taken to be about 
half the weight of water, and therefore they are about 400 times 
heavier than the bulk of air which they displace. If, then, the 
fish were equal in weight to the heaviest material of which we 
know, viz. platinum, it would still be light in comparison to 
the bird in the air. For instance, a cubic foot of platinum 
weighs 20,000 ozs; one of water weighs but 1,000 ozs. 
We have estimated the bird as being half the weight of 
water, equal to 500 ozs. the cubic foot, whilst one of air is only 
about 1*285 ozs. Therefore the instant fall of the fish to the 
bottom could only be prevented by such appendages as wings, 
and the facility to manipulate them, which, however, the density 
of the element in which they exist entirely precludes. 
