394 _ Letter from Sir George Cayley, Bart. 
so clear, that they may be followed by all manufacturers, and ve 
ought to hope that. his work will assist in preserving to France a 
valuable branch of industry, and which a thousand events might 
render one of absolute necessity. 
[To be continued. ] 
_. , LXXXII. Intelligence and Miscellaneous Articles. 
Letter from Sir Grtorce Cay.ey, Bart. 
Green Hill, May 16, 1816 
Siz, — Since I forwarded my second paper to you on the sub- 
ject of Aérial Navigation, I find from a paragraph in the 
Monthly Magazine that Messrs. 8. 1. Pauly civil engineer and 
Mr. D. Egg of No. 32, Strand, are preparing an experiment on 
the steerage of a balloon capable of carrying three or four per- . 
sons. The great bulk inseparable from aérial vessels that are 
capable of carrying any considerable burthen with such speed as 
will render the invention valuable to mankind, is not to be ex- 
pected from individual efforts; but I am glad to find professional 
engineers turning their attention to this subject ; and should any 
efficient subscription take place, I hope the committee ap- 
pointed to regulate it will encourage these exertions ; and that 
by the aid of these gentlemen, in conjunction with the advice of 
the first civil engineers the country affords, experiments upon 
the most efficient scale may soon lead to the establishment of 
the art. 
I remain, sir, 
Your obliged and obedient servant, 
Gro. Cayiy. 
M. de la Roche, in a memoir on. the propagation of sound 
printed in a late number of the Annales de Chimie et de Phy- 
sigue, draws the following conclusions : 
1. That the wind exercises almost no sensible influence on 
sounds heard at short distances, for instance six metres. 2, When 
the distance is greater, the sound is heard far less in the direc- 
tion contrary to that of the wind, than in that of the wind itself, 
The difference seems to be the greater, in proportion as the di- 
stance itself is greater. 
From the approximation of those two propositions, M. de la 
Roche thinks it results, 1. That the law of deerement of sound 
is not the same in the direction of the wind as in that which is 
opposite to it. 2. That the influence of the wind on sound is 
not more exercised on the spot where it has been produced, than 
on every particle of ground which it passes over. 3. That sound 
is heard a little better in a direction perpendicular to that of 
the 
