8 S A C O U S 
tunes; and that thofe are mod didin&ly heard vvhofe dif¬ 
ferences are mod eafily perceivable. 
To this theory, however, though it has a plaufible ap¬ 
pearance, there are drong and indeed infuperable objec¬ 
tions. The very fundamental principle of it is falfe. No 
body whatever, whether eladic or non-elaftic, yields a 
graver found by being (truck with a larger indrument, 
unlefs either the founding body, or that part of it which 
emits the found, is enlarged. In this cafe, the largeft 
bodies always return the graved founds. 
In (peaking of eladic and non-eladic bodies in a mufical 
fenfe, we are not to pudi the didihdtion fo far as when we 
fpeak of them philofophically. A body is mufically elaf¬ 
tic, all of wh'ofe parts are thrown into vibrations fo as to 
emit a found when only part of their furface is (truck. Of 
this kind are bells, mufical drings, and all bodies whate- 
ver that are conliderably hollow. Mufical non-eladics 
are fuch bodies as emit a found only from that particular 
place which is (truck: thus, a table, a plate of iron nailed 
on wood, a bell funk in the earth, are all of them non- 
eladics in a mufical fenfe, though not philofophically fo. 
Whenafolid body, fuch as a log of wood, is druck with- 
a fwitch, only that part of it emits a found which comes 
in contact with the fw itch ; the note is acute and loud, 
but would be no lefs fo though the adjacent parts of the 
log were removed. If, inftead of the fwitch, a heavier 
or larger indrument is made ufe of, a larger portion of its 
furface then returns a found, and the note is confequently 
more grave; but it would not be fo, if the large indru¬ 
ment druck with a fliarp edge, or a furface only equal to 
that of the (mail one. 
In founds of this kind, w’here there is only a fingle 
thwack, without any repetition, the immediate caufe of 
the gravity or acutenefs- feems to be the quantity of air 
difplaced by the founding body ; a large quantity of air 
difplaced produces a grave found, and a fmaller quantity 
a more acute one, the force wherewith the air is difplaced 
dgnifying very little.—What we here advance is confirmed 
by Tome experiments made by Dr. Priedley, concerning 
the mujical tone of eleftrical dilcharges. Thefe drew how 
much the gravity or acutenenefs of founds depends on the 
quantity of air put in agitation by the founding body. 
We know that the noife of the eleftric explofion arifes 
from the return of the air into the vacuum produced by 
the eleftric fladi. The larger the vacuum, the deeper is 
the note : for the fame reafon, the difchp.rge of a muiket 
produces a more acute note than that of a cannon; and 
thunder is deeper than either. 
Befides this, however, other circumdances concur to 
produce different degrees of gravity or acutenefs in founds. 
The fonnd of a table druck upon with a piece of wood, 
will not be the fame with that produced from a plate of 
iron druck by the fame piece of wood, even if the blows 
ihould be exactly equal, and the iron perfectly kept from 
vibrating—-Here the founds are generally faid to aider in 
their degrees of acutenefs according to the fpecific gravi¬ 
ties ordenfities of the fubftances which emit them. Thus 
gold, which is the mod denfeof all metals, returns a much 
graver found than diver ; and metalline w ires, -which are 
more denie than therms, return a proportionabiv greater 
found.—But neither does this .appear to be a general rule 
in which we can put confidence. Bell-metal is denfer 
than copper, but it by no means appears to yield a graver 
found ; on the contrary, it feems very probable, that cop¬ 
per will give a graver found than bell-metal, if both are 
druck upon in their non-eladie date; and we can by no 
means think that a bell of pure tin, the lead denfe of all 
the metals, will give a more.acute fonnd than one of bell - 
metal, which is greatly more denfe.—In feme bodies 
hardmefs feems to nave a confide rabir ebecl. Glafs, which 
is confiderably harder (ban any metal, gives a more acute 
found ; bell-metal is harder than gold, lead, or tin, and 
therefore founds much more acutely ; though how far this 
holds with regard to different fubdances, there arc not a 
fuff id ent number of experiments for us to judge, 
I 
TICS. 
In bodies mufically eladic, the whole fubfiance vibrates 
with the (lighted droke, and therefore they always give 
the fame note whether they are druck with a large or 
with afmall indrument; fo that- (inking a part of the fur¬ 
face of any body mufically eladic is equivalent, in it, to 
driking the whole furface of a non-eladic one. If the 
wdiole furface of a table was druck with another table, 
the note produced would be neither more nor lefs acute 
whatever force was employed; the found wbuld indeed 
be louder in proportion to the force employed, but the 
gravity would remain the fame. In like manner, when a 
bell, or mufical firing, is druck, the w'hole fubdance vi¬ 
brates, and a greater droke cannot increafe the fubdance. 
Hence we fee the fallacy of what is faid concerning the 
Pythagorean anvils. 
Ladly, The argument for the preceding theory, ground¬ 
ed on the production of w'hat are called Jlute-notes on the 
violin, is built on a falfe foundation; for the bow, being 
lightly drawn on an open firing, produces no Jlute-notes , 
but only the harmonies of the note to which the firing is 
tuned. The Jlute-notes are produced by a particular mo¬ 
tion of the bow, quick and near the bridge, and by finger¬ 
ing very gently. By this management, the fame (bunds 
are produced, though at certain intervals only, as if the 
vibrations were transferred to the (pace between the end 
of the finger-board and the finger, indead of that between 
the finger and the bridge. 
Though thefe objections feem fufticiently to overturn 
the foregoing theory, with regard to acute founds being 
the effects of weak drokes, and grave ones of dronger im- 
pulfes, we cannot admit that longer or Ihorter vibrations 
are the occafion of gravity or acutenefs in found. A mu¬ 
fical found, however lengthened, either by firing or he’ll, 
is only a repetition of a (ingle one, vthofe duration by it- 
felf is but for a moment, and is therefore termed inap- 
prelia'ole, like the frnackof a whip, or the explofion of an 
electrical battery. The continuation of the found is no¬ 
thing more than a repetition of this indantaneous inap- 
pretiable noife after the manner of an echo, and it is only 
this echo that makes the found agreeable. For this rea¬ 
fon, mufic is much more agreeable when played in a lar.ge 
hall where the found is reverberated, than in a (mall room 
where there is no fuch reverberation. For the fame rea¬ 
fon, the found of a firing is more agreeable when put on 
a hollow violin than when fadened to a plain board, See. 
—In the found of a bell we cannot avoid obferving this 
echo very didindly. The found appears to be made up 
of didinct pulfes, or repetitions of the (ante note produced 
by the droke of the hammer. It can by no means be al¬ 
lowed, that the note would be more acute though thefe 
pulfes were to fucceed one another more rapidly; the 
found would indeed become more fimple, but would dill 
preferve the fame tone.—In mufical firings the reverbera¬ 
tions are vadly more quick than in bells; and therefore 
their found is more uniform or fimple, and confequently 
more agreeable, than that of bells. In mufical glal- 
fes, the vibrations mud be inconceivably quicker than 
in any bell, or'dringed indrument: and hence they are 
of all others the mod fimple and the mod agreeable, though 
neither the mod acute nor the loaded,—As far as we can 
judge, quicknefs of vibration contributes to the uniformi¬ 
ty, or fimplicity, but not to the acutenefs, nor to the 
loudnefs, of a mufical note. 
It may here be objected, that each of the different 
pulfes, of which we obfgrve the found of a bell to be com- 
pofed, is of a very perceptible length, and far from being 
indantaneous ; fo that it is not fair to infer that the found 
of a bell is only .a repetition of a fingle indantaneous droke. 
feeing it is evidently the repetition of a lengthened note. 
—To this it may be replied, that the inappretiable found 
which is produced by driking a bell in a non-eladic date, 
is the very fame which, being firft propagated round the 
bell, forms one of thefo fnort pulfes that is afterwards 
re-echoed as long as the vibrations of the metal continue, 
and it is Lropoflible that the quicknefs of repetition of any 
found 
