ROT 



II O T 



ROTA, a town of Spain, in the province of Seville, on 

 the coaft of the Atlantic, celebrated for its wine ; 3 miles 

 W. of Puerto de Santa Maria. 



Rota. SeeZARPANi. 



Rota, in Mechanics. See Wheel. 



Rota Arijlotelica, Ari/iot/e's Wheel, is the name of a 

 celebrated problem in mechanics, founded on the motion of 

 a wheel about its axis ; thus called, becaufe firft, that we 

 know of, taken notice of by Ariftotle. 



The difficulty is this. While a circle makes a revolution 

 on its centre, advancing at the fame time in a right line 

 along a plane, it defcribes, on that plane, a right line, 

 equal to its circumference. Now if this circle, which we 

 may call the deferent, carry with it another fmaller circle, 

 concentric with it, and which has no motion but what it re- 

 ceives from the deferent ; which is the cafe of the nave of a 

 coach-wheel carried along by the wheel ; this little circle, 

 or nave, will defcribe a line in the time of the revolution, 

 equal, not to its own circumference, but to that of the 

 wiieel : becaufe its centre advances in a right line as fait 

 as that of the wheel does ; as being in reality the fame 

 with it. 



The matter of fadt is certain ; but how it fhould be, 

 feems a myitery. It is obvious that the wheel, advancing 

 during the revolution, muft defcribe a right line equal to its 

 circumference ; but how would the nave, which revolves 

 like the wkeel, defcribe a right line fo much greater than its 

 circumference ? 



The foiution Ariftotle gives is no more than a good ex- 

 plication of the difficulty. Galileo, who next attempted it, 

 has recourfe to an infinity of infinitely little vacuities in the 

 right line defcribed by the two circles ; and imagines that 

 the little circle never applies its circumference to thofe va- 

 cuities ; but in reality only applies it to a line equal to its 

 own circumference ; though it appears to have applied it to 

 a much larger. 



But it is evident, that this is all gratis dictum. The va- 

 cuities are imaginary ; and why does not the great circle 

 apply its circumference to them ? Laftly, the magnitude of 

 thefe vacuities muft be augmented or diminished, according 

 to the different proportion of the two circles. 



F. Tacquet will have it, that the little circle, making its 

 rotation more (lowly than the great one, does on that ac- 

 count defcribe a line longer than its circumference ; yet 

 without applying any point of its circumference to more 

 than one point of its bafe. But this is no more allowable 

 than the former. 



The attempts of fo many great men proving vain, M. 

 Dortous de Meyran, a French gentleman, had the good 

 fortune to hit on a foiution, which he fent to the Royal 

 Academy of Sciences ; where being examined by Meffrs. 

 de Louville and Saulmon, appointed for that purpofe, they 

 made their report, that it was fatisfa&ory. The foiution is 

 to this effect : 



The wheel of a coach is only acted on, or drawn in a 

 right line ; its circular motion or rotation arifes purely from 

 the reiiltance of the ground on which it is applied. 



Now this refiftance is equal to the force with which the 

 wheel is drawn in the right line, inafmuch as it defeats that 

 direction ; of confequence, the caufes of the two motions, 

 the one right, the other circular, are equal ; and, therefore, 

 their effects, /. e. the motions, are equal. And hence the 

 wheel defcribes a right line on the ground equal to its cir- 

 cumference. 



As for the nave of the wheel, the cafe is otherwife. It 

 is drawn in a right line by the fame force as the wheel ; but 



it only turns round becaufe the wheel turns* and can only 

 turn with it, and at the fame time therewith. 



Hence it follows, that its circular velocity is lefs than that 

 of the wheel in the ratio of the two circumferences ; and, 

 therefore, its circular motion is lefs than its rectilinear 

 one. 



Since then it neceffarily defcribes a right line equal to 

 that of the wheel, it can only do it by Aiding, or what they 

 call the motion ot rotation ; that is, a part of the circular 

 nave cannot be applied to a part of a right line greater 

 than itfelf but by Hiding along that part, and that more 

 or lefs, as the part of the nave is Lefs than that of the 

 circle. See Rotation. 



Rota is alfo ufed for a particular court of jurifdiftion in 

 Rome, ettablifhed for taking cognizance of beneficiary mat- 

 ters, &c. 



The rota confills of twelve doftors cliofeu out of the four 

 nations of Italv, France, Spain, and Germany ; three of 

 them being Romans, one a Florentine, one a Milanefe, one 

 of Bologna, one of Ferrara, one a Venetian, one a French- 

 man, two Spaniards, and one a German ; each having four 

 clerks or notaries under him. 



Their office is to. judge of all beneficiary caufes, both 

 within Rome, and throughout the itate of the church, in 

 cafe of appeal, and of all civil proceffes which are for above 

 five hundred crowns. 



They are alfo called chaplains of the pope, as fucceeding 

 the ancient judges of the laci'ed palace, who held their court 

 in his chapel. 



The denomination rota, •wheel, fome will have derived 

 hence, that they officiate by rotation ; others, becaufe the 

 moit important affairs of the Chriltian world turn upon 

 them. Du-Cange derives it from rota porphyretlca, becaufe 

 the pavement of the chamber where they formerly fat was 

 of porphyry, and fafhioned like a wheel. 



Rota, La, in Biography, an admirable bravura finger 

 in the Incurabili Conlervatorio at Venice, in 1770, under 

 the regency of Galuppi. 



ROTAB, in Geography, a river of Saxony, which runs 

 into the Saale, three miles S. of Lena. 



ROTACE.AL, in Botany, the 20th natural order among 

 the Fragmenta of Linnjeus, named from rota, a wheel, in 

 allulion to the form of the corolla, which is wheel-lhapcd, 

 rotata. No commentary upon this order is found in the 

 lectures of Linnseus, publifhed by Gifeke. The genera 

 ftand thus ; Trientalis, Centuncuhu, Anagallis, Lyfimachia, 

 Phlox, Exarum, Chlora, Gentiana, Swertia, Chironia, and 

 Sarothra. To which are fubjoined, in a feparate fection, 

 Afcyrum, Hypericum, and Cijlus ; thefe furely have little 

 affinity to the reft. 



ROTACH, in Geography, 1 river of Bavaria, which 

 runs into the Maine, near Lichtenfels, in the bifliopric of 

 Bamberg. 



ROTA I, or Rotte, a fmall ifland in the Eaft Indian 

 tea, where a Dutch faCtor refides, who trades with the na- 

 tives in the chief article of their produce, which is fugar. 

 The north end of this ifland, and the fouth end of Timor 

 (which fee), lie N. i E. and S. \ W., and are about three 

 or four leagues diftant from each other. At the weft end 

 of the pailage between Rotte and Semau (which fee), are 

 two fmall iflands, one of which lies near the Rotte fhore, 

 and the other oft' the fouth-weft point of Semau, with a 

 good channel between them, about fix miles broad. The 

 ifle of Rotte has not fo lofty and mountainous an appearance 

 as Timor, though it is agreeably divcriiiied by hill and valley. 

 On the nortli fide are many fandy beaches, near which grow 

 fome trees of the fan palm ; but the far greater part was 



covered 



