62 Translation of Rey*s Essays. 



out and fill the bladder. Let another similar bladder be filled and 

 fitted in like manner, and so on to the end. I say that the last 

 bladder will be heavier than the first; whoever doubts it, let 

 him make the experiment, proceeding exactly as directed. By 

 this train of thought my mind elevates itself to greater things, 

 which, however, I shall not mention now, as they are irrelevant 

 to this subject, and difl^icult not only to practise but even to 

 understand. I come to another demonstration, by which the 

 truth that I defend will be more than evident (plus que visible.) 

 Plant a cannon directly on its breech, its muzzle pointing 

 upwards, and throw into it a red-hot ball of the size of its 

 bore. It is certain that the air contained in the cavity of the 

 gun is so thin in substance and small in quantity, that the ball, 

 in passing, will impress on it its full degree of heat ; notwith- 

 standing this, if you put your hand into the muzzle, you will 

 easily keep it there at first, but in a short time you will be 

 unable to do so ; not that the air has increased in heat, for it 

 will rather have decreased, as well as the ball which gradually 

 cools ; but, because being thickened by the separation of the 

 more subtle parts of a large quantity of air which will 

 rush out quickly, {d'un abondance d'air, qui s'y porfera grand 

 erre) it will act more powerfully, as I have said elsewhere. 

 In the second place, the air which will be seen trembling above 

 the muzzle of the gun, (which does not take place at first,) 

 compels us to confess, that it is thickened ; for, it cannot be 

 said that these are vapours or exhalations rising from the gun, 

 for every thing about it is too dry and solid to suffer the escape 

 of any of its own substance. Thirdly, if the air were not 

 thickened above the muzzle it would not render the objects 

 beyond it, seen through it, confused. Nor can my opponents 

 excuse their disbelief on account of the tremulous motion 

 (brandillemeyit) of the air, since I distinctly see that lady's 

 beauties through the air, which she agitates with her fan, and 

 also all sorts of objects through an atmosphere violently dis- 

 turbed by the north wind, when it blows and whistles bois- 

 terously. Lastly, if a flock of wool much extended (esparpillf) 

 be placed over the muzzle of the gun, it will not descend; and, 



