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XV. Ona New Mufical Infirument invented by Dr. CHLAD=+ 
ni; with fome Experiments on- the Vibrations of Sonorous 
Bodies. , 
ie the month of February laft, Dr. Chladni of Witten- 
berg, well known by his various publications on. philofophi- 
cal fubjeéts, and particularly his experiments on found, per- 
formed before a numerous aflembly at Vienna, on a new 
inftrument he has invented, and to which he gives the name . 
of Expbon. This inftrument has nothing in common with 
the Harmonica but the glafs. It confifts of forty-one im- 
moveable parallel cylinders of glafs, of equal length and 
thicknefs. Its conftruction, tone, and the method of play-, 
ing it, are totally different from thofe of the Harmonica. 
At the fame time Dr. Chladni made feveral curious experi- 
ments on the vibrations of fonorous bodies, by which he 
fhewed that fand or faw-duit, firewed over thefe bodies 
while vibrating, forms different regular figures, according to 
cireumftances. As it may afford fatisfaCtion to our philofo- 
phical readers to know the manner in which thefe experi- 
ments may be partly repeated, we fhall fubjoin the follow- 
ing fhort account: Take a {quare piece of glafs, pretty 
thin, fuch as that ufed for windows, about four or five 
inches over, or even more. Smooth it at the edges on a 
grinding-ftone; firew a little faw-duft over its furface, and 
lay hold of it gently with the thumb and fore-finger of the 
left-hand, fuppofing that you lay hold of it by the middle. 
With the right-hand rub a violin bow foftly againft one of 
the edges of the glafs, drawing it cither up or down, in a 
direction almoft perpendicular to its furface, and you will 
then fee a tremulous movement and the whole duit leap 
about. Ifthe bow is exactly in the middle of one of the 
fides, the duft will arrange itfelf almoft in the direction of 
the two diagonals, dividing the fquare into four iofceles 
triangles, If the bow be applied at a quarter only of the | 
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