4 8

Of Winds and Sounds.

From the fourth Property of the aeridPulses we have the Origin of the various

Degrees

Sphere DE = io Feet, the Square of which is ioQ>which multiplied by 0,7854, gives 78,54 square Feetfor the Area of a great Cirle AHEFC. And there-fore 4 times that Area, viz. 4X 78,54= 314,16 = squareFeet in the Superficies of the Aerial Sphere. If nov^the Diameter AC of the End of a Trumpet be oneFoot, its Area will be 0,7854; but, 7854 : 314,

:: 1 : 400, therefore the Air at the Distance of B Pwill be agitated by means of the Trumpet, with *Force 400 times greater than by the bare Voice alone.

5. Again, ’tis farther evident how Instruments of

this Form assist the Hearing greatly ; for the weak an"languid Pulses of Air being received by the large En“of the Tube, and greatly multiplied and condensed b/the tremulous Motion of the Parts of the Tube and A**jagitated by them, are conveyed to the Ear by the fin**End, and strike it with an Impetus as much gre-tetthan they would have done without it, as the Area 0the small End at B is less than the Area of the larg eEnd AL. ... n-a

6. From what has been said, 'tis evident the En e£of the Tube in magnifying Sound, either for speakingor hearing, depends principally upon tfie Length ofTube. But yet some Advantage may be derived

the particular Form or Shape thereof. Some very etpi Inent Philosophers have proposed the Figure which * Smade by the Revolution of a Parabola about its A* 1 ®as the best of any ; where the Mouth-Piece is placein the Focus of the Parabola, and consequently the » 0 ^norous Rays will be reflected parallel to the Axis of 41Tube. See the Figure of such a Tube in Mus " e11Ircek’s EJsai de Physique. . j

7. But this parallel Reflection seems no way eflenti*^to the magnifying of Sound ; on the contrary, *tpears rather to hinder such an Effect, by preventing * ^infinite Number of Reflections and Reciprocations ^Sound, in which, according to Sir Isaac Newton, ^