EFFECT OF SOUND ON THE BAROMETER. ]$1 



V. 



On the Ejfi& of Sound upon the Barometer. By Sir Henry. C. 

 Englefield, Bart. F. 11. S. (From the Journals of the 

 Royal Inftitution, No. 9. J , 



•JDuRING the time I fpent at Bruflels in the year 1773 and Whether the ba- 



1774., it occurred to me, that the effect of found on the barome- JJgJjL fon ^ 



ter had not, to my knowledge, been attended to ; and that it rous undulation. 



was by no means certain, whether that inftrument was capable 



of being fenfibly affected by thofe elaftic vibrations caufed in 



the atmofphere, by the perculfion of a fonorous body. I 



thought the idea worthy of being purfued, and the means of 



making fatisfactory experiments were moft opportunely in my 



power. 



The found of a very large bell appeared to me the mod The bell prefer- 

 powerful, and at the fame time to be approached with the red for ex P en " 

 greateft fecurity and eafe to the obferver. The explofion of 

 artillery, belides the very difagreeable fmokeand danger of the 

 xecoil, might be objected to, on account of the fudden produc- 

 tion of elaftic and heated vapour, which might, independent of 

 the found, inftantaneoufly alter the ftate of the atmofphere, 

 and thereby lead the obferver into very great and unavoidable 

 errors. 



Every one who has been in the Low Countries muft know, Large bells In the 

 that very large bells, and immenfe numbers of them, are the Netherlands » 

 pride of their churches ; and that they are rung' quite out, not 

 tolled, on every great feftival. The great bell of the collegiate 

 church of St. Gudula, at Bruflels, weighs, as I was told, fix- 

 teen thoufand pounds, and on this I determined to found my 

 experiment. 



Two objections only could be made to the refult of this ex- Whether thefe 

 periment, the one, that the motion of the bell might caufe a vi- would produce 



jrrc£u]ariCY dv 



bration in the walls of the building, which would hinder the agitating the 

 placing the barometer in a ftate of repofe ; the other, that the buildin g or the 

 twinging fo large a mafs with a confiderable degree of velocity, 

 might of itfelf agitate the air fo as to caufe vibrations in the 

 mercury totally independent of found. 



The ftrength of the walls of the fteeple, and the manner of Obfemtibns, 

 hanging the bell, which was contained in a frame of limber, 



founded 



