318 SOUND. 



sound reach the observer's ear in the same space of time 1 

 11. Whether all sorts of sounds, as those of guns, bells, 

 hammers, &-c, have the same degree of motion ? 12. 

 Whether the different strength of gunpowder vary the 

 motion of sound ] 13. Whether sound pass over the 

 same space in the same interval of time, on the tops of 

 high mountains, and in the bottoms of valleys ; or in the 

 highest and lowest parts of the atmosphere ? 14. Whether 

 sound in acclivities and declivities have the same degree 

 of motion; or whether it descends from the top to the 

 foot of the hill with the same velocity, as it ascends from 

 the foot to the top of the same 1 15. Whether sound 

 move swifter in the beginning, and slower at the end; as 

 is the case in a great many other violent motions 1 16. 

 Or whether it be not rather equable 1 viz. moving in 

 half the time, over half the space ; in a fourth part of the 

 time, a fourth part of the space, &c. 17. Whether 

 sound have the same degree of motion in all climates, 

 both north and soudfr, in England, France, Italy, Germany, 

 &,c 1 18. Whether sound pass from one place to another 

 in a straight line, or in the shortest way ; or whether it 

 move along the superfices of the intermediate earth ? ' 

 The answer to all these questions may be given in a sin- 

 gle sentence. The velocity of sound through the air, is 

 under all circumstances the same. A wind will of course 

 retard or accelerate it, according to the velocity of the 

 wind. 



On account of 'the variation in the results of previous 

 experiments, the French [Academy of Sciences, in 1728 

 undertook them anew. They stationed a cannon at 

 Monthlery, and noticed the report at Montmartre near 

 Paris, a distance of 2 miles, 4076 feet. They found 

 the sound to have a uniform velocity of 1107 feet in a 

 second ; so that it was merely weaker at a greater dis- 

 tance, but passed successively through equal spaces in 

 equal times. The velocity seemed to be affected by no 

 circumstances but the direction and force of the wind. 

 It was the same in rainy as in settled weather. The 

 wind occasioned no variation when it blew in a direction 

 perpendicular to a line drawn from the cannon to the 

 observer, But when both were in the same direction, it 



