ON INSTRUMENTS FROM ITALY. 131 



struck me, and which would be able to be obtained, in case the pro- 

 gress of sound were always equable, or at least if the proportional rate 

 at which it advanced were known. 



" Serenissimo Granduca, If the velocity of the motions of all 

 sounds, both loud and soft, powerful and weak, are perfectly equal, as I 

 am convinced they are, and are likewise unaffected by any change of the 

 air or gust of wind, either favourable or unfavourable ; and if moreover 

 the progress of any sound is equable, as I believe to be the case that 

 is, that in any given equal spaces of time the distances traversed are 

 the same (as the Discussion has persuaded me must follow), most 

 useful and most curious consequences can be drawn. 



" Let a most exact experiment be made of the time which the sound 

 of a bomb (exploded, say, at the precise distance of three miles) takes 

 to reach our ears, and having accurately found by measurement the 

 time which it takes, we can say a third of a minute prime of an hour ; 

 or without caring to know what part, of an hour the time may be, we 

 can say that it took forty vibrations of such a pendulum ; and from 

 this observation alone we shall obtain the following, and many other 

 results. And first of all, we shall be able expeditiously to know how 

 far from us anything making a sound is, provided we can see the blow 

 given and that the sound reaches our ear. 



" It will be possible, without using any instruments (which for the 

 most part prove incorrect), without moving from one spot, to know the 

 distances of towns, villages, castles, c., provided they be seen, and 

 that the sound of a blow or a shot be heard at such a distance. Plans 

 of great countries can thus be made, by merely' knowing the angles, 

 and with very great saving of positions ; it will be equally effective 

 in plains as on mountains, where great difficulty is experienced on 

 account of the imperfections of the instruments, c. 



" It will be possible to ascertain the distance of an army from any 

 place, to know how far off batteries are stationed, and obtain many 

 other similar advantages in time of war. 



" Moreover, we shall be able to know how far distant from any place 

 on land or at sea an island may be, or a ship, or a fleet, or how far 

 off a naval battle is taking place ; we shall be able to measure the 

 distance bct\vecn two ships, or two islands, or two rocks, when they 



