4 1 4 Expcrimitits oil the TranfmiJ/ion if Swnd. 



Inti.'y'ty of Smnd tbferved in differtiit Fluids. 



1. In the air ferviiig as the term of comparifon, it ceafes to belie.ird at the dif- 



tance of — — 8 



2. In the water, at that of — — — 2o 



3. Oil-olive 16 



4. Oil of turpentine ■ ■ ]4 



5. Spirit of wine ■ ■ 21 



It is proper to obfervc, that on repeating thefe trials I obferved fome variations in tlic in- 

 tenfity, which appeared to depend on the organ of fenfe or accidental noifcs. 



From the experiments made upon liquids, it follows: — i. That thcfc as well as folids do 

 tranfmit founds much belter than air, and that even the fat oils are not to be excepted>*. 



2. That each fluid upon trial is found to modify the found in a peculiar manner. 



3. Philofopliers maintain the opinion that found is propagated in the air hy means of 

 certain motions or undulations, which the tranfparence of that fluid prevents our feeing. 

 Wy experiments with fluids which do not elude the fight, and in which no motion was 

 perceived, notwithftanding the very effectual tranfmiffion of found, may render this in fome 

 rtfped doubtful. 



4. Laftly, the experiments on folids, fluids, and thofe I have publiflbed onthegafesi, 

 afford the probable conclufion that all mediums produce particular modifications in the tone 

 (timbre) and the intenfity of found ; or otherwife, that the fame found varies as often as it 

 paffes through a difl^erent medium. I fliall now pafs to the experiments which conftitute 

 tlie fecond part of this memoir. 



PART 11. 



EVERY one has obferved, that if a watch be placed upon a table, the found is very evi- 

 dently increafed. The difference between the found of a tuning-fork, when it vibrates 

 without being placed in contact with any folid body, and that which it affords when its 

 handle is preffed againft a folid body with a large furface, is alfo well known. The experi- 

 ments related in the former part of this memoir having led me to expeQ that the increafe 

 offeree and harmony in thcfe circumftances was owing to the property poffeffed by wood 

 of propagating found better than the external air, and modifying its tone ; I determined to 

 afcertain the truth by experiment. 



The different powers 1 had obferved in wood and marble, with regard to the propagation 

 of found, appeared proper to throw fome light on this important queflion. In fadt, if the 

 modifications of the found of the tuning-fork and the watch, when placed on a table of wood, 

 be owing to the energy with which this fubftance tranfmits the found, and the marble pro- 

 pagating it very weakly, it would follow that a table of marble ought not to fortify the 



• Morhof, Sieut. pag. 104. affirmed that fat oils could not tranfmit fonorous modulatioiit. P. 

 f Loco citato. 



' 2 ' found, 



