VOL. XXVI.] PHILOSOPHICAL TRANSACTIONS. 385 



the sound of a hammer) and found that the sound of both reached me in the 

 same time; and that it passed over ^, 4-, and i of the same space, in ^, 4-, and 

 4- of the same time. And as to intense and languid sounds, I am also per- 

 suaded that they pass through the same space in the same time; as appears in 

 some measure from the following experiments. At Tilbury Fort were fired a 

 gun or two, and a great mortar, into which the powder was well rammed : the 

 report of all these reached me, at about 3 miles off, at the same time. After 

 sun-set also, some muskets, sakers, and mortars were discharged on Black- 

 heath : I could not hear the muskets, either by reason of the great distance, or 

 because the air was not clear enough ; yet I heard the sakers and mortars in the 

 same space of time, though the report of the mortars was more languid and 

 weak than that of the sakers. 



^7. Of the equable Motion of Sound. — And this I found to be the same with 

 what the academy Del Cimento had determined; for sounds pass over half the 

 distance in half the time, and a fourth part of the distance in a fourth part of 

 the time, and so on; as appears from the examples in the following table : 



Table of Experiments on Sound. 



„, , .L 17 1 • Number of Vi- Distance of places, ^. ,. ^ 



Places where the Explosion brations of the ^ r^ . \^ a ^Jf^^'^^^^^f 



was made. nendulum ^ Tngon. . . By Sound. the wmds. 



Miles. Miles. 



At Horn-church 9 - . O.988 . . transverse. 



North Okendon church. . 18-^ .. 2.004 .. 2 .. transverse. 



Upminster mill { H' ..}2.4 .. { ^- j " • ^^"""g- 



*^ '^ 23 -' *^ 2.48 . . snow, trans. 



Little Warley church 274- ..3 .. 2.97.. strong, fav. 



Rainham church 334- . . 3.58 . . 3.59 . . transverse. 



Alvely mill 33 . . 3.58 . . 3.57 • • transverse. 



Dagenham church 35 . . 3.85 . . 3.78 . . favouring. 



South Weal church .... 45 . . 4.59 • • 4.86 . . transverse. 



East Thorndon church . . 464. . . 5.O9 . . 5.03 . . rather fav. 



Barking church 704- . . 7 '7 • • 7.62 . . favouring. 



Blackheath II6 . . 12.5 . . 12.55 . . transverse. 



I measured very accurately, either with a rod, or by trigonometry, the 

 distances set down in this table, of the places from Upminster, where I made 

 my observations, the truth of which, and the goodness of my instruments, ap- 

 pear from the near agreement between the distances measured in that manner, 



VOL. V* 3 D / 



