On Air Balloons, ^ 



be able to correct them ; and, in order to incite others to the 

 trial, I will here resolve such difficulties as may be opposed to 

 the practical operation of this discovery." 



He then proceeds to state a safe mode of exhausting the air ; 

 and remarks, that some persons may suppose that, from the 

 violence of the rarefaction, the balloon may either be broken, or 

 so bent, as to destroy its rotundity ; but in answer to this ob- 

 jection, he replies, that the globes, being perfectly spherical, 

 the air will compress every side alike ; so that it is more likely 

 to strengthen than collapse them, as his experience taught 

 him with glass globes, which, Avhen not round, were easily de- 

 stroyed by the egress of air ; but when perfectly so, then they 

 resisted all pressure. Next, he proposes, in order to be secure 

 of this form, that they shall be constructed, first, as two half 

 globes, and then soldered up as one balloon. Again, with respect 

 to the question as to what height this vessel may ascend, since, 

 if they could be raised to the surface of our atmosphere, it na- 

 turally follows that the men in it would not be able to respire ? — 

 to this he replies, that it could only be supported at a certain 

 height, where the atmosphere was sufficiently dense to sustain 

 it, and that she may be loaded according to the altitude in- 

 tended to sail in ; and would have the power to decline, by 

 merely opening the key of the valve, so as to introduce a certain 

 quantity of common air, and thus they could, at any time, 

 descend. 



Again, it might be objected, that she could never sail in any 

 fixed direction, as ships do, who have a resistance from the 

 water ; but, says the author, ** although air does not resist like 

 water, it still makes some resistance, and if it has less than 

 water, there is less to overcome in sailing; and as there is 

 always some wind, however weak, there will probably be always 

 enough to propel the vessel, and with respect to its being con- 

 trary to the course they mean to keep, he has a contrivance to 

 allow the mast to rotate with its sail in all directions." 



Lastly, it may be objected, says he, that it will be difficult to 

 overcome the violence of the wind, which may drive them 

 against the mountains — those formidable rocks in this ocean 

 of air, which might overset them ; but here, like all sanguine 

 inventors, he finds an easy answer, which is, that the four 



JAN.— MARCH, 1828. D 



