VOL. XXVI.J PHILOSOPHICAL TRANSACTIONS. 3Q3 



son, walking or riding, may easily outrun them, as is apparent to sense; for as 

 often as we stop our pace, we perceive a gentle gale softly fanning us ; but if we 

 walk with the same pace, that the wind moves, we hardly feel any at all ; if 

 faster, we find that, instead of accompanying and blowing with us, it blows in 

 our faces : so that when the atmosphere is quite calm, if we are walking or 

 riding, we perceive a gentle gale, corresponding to the motion we are in ; and 

 the gale of wind, or flux of air, moves with the same degree of velocity, we 

 find it affect us, while we stand still. 



From these observations on the velocity of winds, we may make many use- 

 ful remarks ; especially, give one good reason, why the mercury ascends and 

 descends so long before fair weather, or rain. Since sound is swifter than wind, 

 it is plain, that those parts of the atmosphere, whereon it is impressed or con- 

 veyed, are not the same with those of which wind consists, but some other 

 more aethereal and volatile particles ; for the swiftest wind does not move above 

 60 miles in an hour, whereas sound moves in the same time upwards of 700 

 miles. But if it should be objected, that winds either accelerate or retard the 

 motion of sound ; it may be answered, that this does not proceed from the pro- 

 per flux or tendency of the windy particles alone, but rather from the joint and 

 concurring motion of both the gross and aethereal particles of the atmosphere ; 

 which course or direction of motion, should it favour the undulations of sound, 

 its appulse, it is very probable, would thereby be accelerated, but contrary 

 thereto, it would be retarded. 



§ 13. On the Felocity of Sounds. — From what has been said above, I firmly 

 conclude, that sound is propagated with this degree of velocity, viz. that in 9 

 half seconds and -^ it moves the space of a mile, or 5280 English feet ; or, 

 which is the same thing, 571 feet in a half second of time, or 1142 feet in a 

 whole second. Thus, sound moves through the above space, if the flux of the 

 atmosphere or wind be transverse or across, and is its mean motion ; but should 

 the wind increase the rapidity of sound, it is impossible that it may move up- 

 wards of 600 feet in a half second of time ; or, on the contrary, should it 

 retard sound, it may move not above 56o feet in the same time. 



All the above-mentioned observations and experiments may be useful, 1. To 

 the philosopher, for investigating the nature of sound, and explaining its ab- 

 struse phaenomena. 2. To the sailor, for discovering the distances of ships, 

 either under sail or at anchor, and of land seen a great way off^; all which he 

 may know with ease and certainty, by the firing of guns. 3. To the soldier, 

 for finding the distance of an enemy's camp, and that of a city, castle, or 

 arsenal, &c. that is to be besieged, in order to place his batteries, and direct his 



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