2p6 The fhQatural Hiftory 



imprints both figure and motion into it, In the ftrfl Cafe (perCaf. i. 

 H,p.\. Trine, i.) orelfe communicates its motion only, inthey- 

 cond, (per Mat. 2.) whereby the next undulation of Air, from the 

 touched firing, taking it juft at its return, and in like manner the 

 confequent ones, and moving it as before, they continue their 

 vibrations together, pajfibas <equi4, Q^ E. D. 



Prop. 2. If the leffer of Wo Oftaves BC, be touched Fig. 7. 

 each half of the greater C2, 2D will anfwer it, the middle 2 

 fiandingslill which he thus demonftrates. 



About CD wraploofly 3 mrrowftrips of paper, one in the middle 

 2, the other betwixt Ci and 2D (exemp.gr. in p and q) then with 

 the finger or bow ftrike BC, or any part of it, and you will fee the- 

 papers in p q, dance and play up and down and about the firing, 

 'twixt Ci and iD, but that in 2 ftand ftill. Whence it is evident, 

 that CD moves in its two halves, by two difiincl motions. Which 

 he thinks occafioned by the arched Airs, nulling with the force of 

 BC againft all CD, and moveing it fomwhat forward out of its 

 place ; but finding it of a difproportionate lengtb, bignefs, and 

 tenfion, to be excited by fo quick vibrations, as may correfpond 

 with thofe of BC, and the undulations whereinto they ftrike the 

 Air (by which alone it caufes any firing to vibrate) per Mat. 3. 

 the fecond undulation of the Air from BC meets CD juft at its re- 

 turn (CD's vibrations to BC's, and the Airs undulations caufed 

 thereby, being as 1 to 2) whereby it is beat back, and rebounds 

 from 2 towards BC } when the third undulation from BC occurring, 

 forces it forward again ; whereupon (not being able to move 

 backward nor forward) the undulations break and roll away to 

 each fide, towards CandD. Which parts Ci. 2 D being Vnifons 

 to BC, per Princip. 2. it eafily moves them per Prop. 1. and fo, 

 (though Des Cartes denys it ) they apparently vibrate mpq (vid. 

 Fig. i$. j by two difiinft motions, Q^E. D. 



Prop. 3 . If the greater of two Oftaves CD be touch on either of 

 its halves C2. 2D. all the leffer will anfwer it, but if on the 

 middle 2 itwillfiir no wbzre. Which is thus demonftrated. 



About BC, Fig. y. wrap loofly onefirip of paper, then with the 

 finger or bow, ftrike CD on either half, Ci or 2 D, and you will fee 



1 



Pes cartes Mu/. Comp- f- 5. 



the 



