803
T R IJ
°f silver. The ancients had various instruments of the trumpetkind, as the tuba, cornua, Sec. Moses , as the scripture informs us,made two of silver to be used hv the priests: and Solomon, Jo-sephus tells us, made two hundred like those of Moses , and for thesame purpose. The modern trumpet consists of a month-piece,near an inch across. The pieces which conduct the wind arecalled the brandies; the parts in which it is bent, the potences;and the canal between the second bend and the extremity, the pa-vilion ; the rings where the brandies take asunder, or are solderedtogether, the knots, which are five in number, and serve to coverthe joints.
Trumpet, Speaking, is a tube from six to fifteen feet Ions,made of tin, perfectly straight, and with a very large aperture ; themouth-piece being large enough to receive both lips. The speak-ln g-trumpet, or stentorophonic tube, as some call it, is used formagnifying sound, particularly that of speed), and thus causing itto be heard at a great distance. How it does this will be easy (ounderstand from the structure of it, thus illustrated : Let ACB bethe tube, BD the axis, and B the mouth-piece for convoying thevoice to the tube. (Plate. CLXII. fig. 2.) It is then evident,"men a person speaks at B in the trumpet, the whole force of hisVoice is spent upon the air contained in the lube, which will bea gitaled through the whole length of the tube ; and jay various re-flections from the side of the tube; to the axis, the air along themiddle-part of the tithe will be greatly condensed, and its moinen-tum proporlionably increased, so that when it comes to agitate theair at the orifice of the tube AC, its force will be as much greaterIhan vvhat it would have been without the tube, as the surface of asphere, whose radius is equal to the length of the tube, is greaterIhau the surface of the segment of such a sphere, whose base is theorifice of the tube. See Acoustics. For a person speaking at"» vvithout the tube, will have the force of his voice spent in ex-iting concentric superficies of air all around the point B; and"'hen those superficies or pulses of air are diffused as far as Devery way, it is plain the force of the voice will he diffus-ed through the whole superficies of a sphere whose radius is
• '"the trumpet it will be so confined, that at its exitit will ie only diffused through so much of that spherical surfaceof air, as corresponds to the orifice of the tube. But since theforce is given, its intensity wdl be always inversely, as the numberof particles it has to move ; and tnerefore in the tube it will be tothat without, as the superficies of such a sphere to the area of thelarge end of the tube nearly. To make this matter yet plainer by-calculation, let BD = 5 feet, then will the diameter of the sphereDE = 10 feet, the square of which is 100, which, multiplied by0,7854, gives 78,54 square feet for the area of a great circleAH EEC. And, therefore, four times that area, viz. 4x78,54 =314,16 square leet in the superficies of the aerial sphere. If nowthe diameter AC, of the end of a trumpet, in one foot, its area willBe 0,7S54 : but -7S54 : 314.16 :: 1 : 400, therefore the air at thedistance of BD, will be agitated by means of the trumpet, with a,force 400 times greater than by the bare voice alone. Again, it isfarther evident how instruments of this form necessarily assist theBearing; for tiie weak and languid pulses of the air being receivedBy the large end of the tube, and greatly multiplied and con-densed by the tremulous motion of the parts of the tube, and aira 8jtated by them, are conveyed to the ear by the small end, andstl 'ke it with an impetus as much greater than they would have
* °ne without it, as the area of the small end at B is less than thearea of the larger end AC. From what has been said, it is evi-. "t the efl'ect°of the tube in magnifying sound, either for speak-
0r hearing, depends chiefly upon the length of the tube. Butyet some advantage may be derived from the particular shape.°nie very eminent philosophers have proposed the figure which is'tide by the revolution of a parabola about its ax.-r, as the best ofo.V, where the mouth-piece of the parabola, and, consequently,g e sonpious rays will be reflected parallel to the axis of the tube.f V i ll 'is parallel reflection seems no way essential to the magni-an " «-° f Souml : on die contrary, it appears rather to hinder suchC by preventing the infinite number of reflections and re-
its <:atl<n ' s of sound ; in which, according to Sir Isaac Newton ,in p^SO'entation principally consists. For all reciprocal motion,lie,,7- v ri lur| '> is augmented by its generating cause, which isp ( .'. ‘fcniulous motions of the parts of the tube. In every re-pnt f \' ! ." l ? n * 'herefore, from the sides of the tube, the agitations and
v-,, 0 fonfined air must necessarilv be increased ; and conse-iv.—j{ 0 . 212 ,
T ft U
quently this augmentation of the impetus of the pulses must beproportional to the number of such repercussions ; and therefore,to the length of the tube, and to such a figure as is most productiveof them. Whence it appears that the parabolic trumpet is of allothers the most unfit for this purpose, instead of being the best. Butthere is otu- thing more which' contributes to the augmenting ofthese agitations of air in the tube, and that is the proportion whichthe several portions of air bear to each other, when divided bvtransverse sections, at very small, but equal distances, f'oin oneend of l!le tube to the other. I’hus, let Uiore several divBions bemade at the points a, b, c, d, e, &c. (fig 3,) which let the right linesak, bl, cm-, dn, See. be taken in geometrical proportion. Thenwill the portions of air contained between B and a, a and b, b andc, c and d, Sec. be very nearly in the same proportion, as being; in tbe S3me ratio with their bases, when the points of division areindefinitely near together. But when any quantity of motion iscommunicated to a series of elastic bodies, it will receive thegreatest augmentation when those bodies are in geometrical pro-portion. Therefore, since the force of the voice is impressed upon,and gradually propagated through, a series of ela-tic portions of airin a geometrical ratio to each other, it shall receive the greatestaugmentation possible. Now, since by construction it is B a — abc= be ~ cd, Sec. and also ak : bl: : bl ; cm :: cm : dn, and so on ;
. therefore, the points k, l, m, n, o, p, k, r, s, will, in this case, form •that curve line which is called the logarithmic curve ; consequentlya trumpet, formed by the revolution of this curve about its axis,will augment the sound in a greater degree than any other figuredtube whatever.
Trumpet, Listening or Hearing, is an instrument inventedby Joseph Landini, to assist the hearing of persons dull of that fa-cility, or to assist us to hear persons who speak at a great distance.Instruments of this kind are formed of tubes, with a wide mouth,and terminating in a small canal, which is applied to the ear. Theform of these instruments evidently shews how they conduce toassist the hearing, for the greater quantity of the weak and languidpulses of the air being received and collected by the large end ofthe tube, are reflected to the small end, where they are collectedand condensed ; (hence entering the ear in Ibis condensed state,they strike the tympanum with a greater force than they couldnaturally have done from the ear alone. Hence it appears thata speaking-trumpet may be applied to the purpose of a hearing-trnmnet bv turning the wide end towards the sound, and the nar-row end’ to the ear. See Plate CLXII. fig. 4 and 5 for particu-lar forms of this instrument. . .
Trumpet, Marine, is a musical instrument consisting of threetables, which form its triangular body. It has a very long neckwith one single string, very thick, mounted on a bridge, which isfirm on one side, but tremulous oil the other, it is struck by abow with one hand, and with the other the string is pressed or stop-ped on the neck by the thumb. See Plate CLXII. fig. 6, 7, and8. It is the trembling of the bridge, when struck, that makes itimitate the sound of a trumpet, which it does to that perfection,that it is scarcely possible to distinguish the one from the other. Andthis is what has given it the denomination of trumpet marine, though,in propriety, it be a kind of monocliord. Of tbe six divisiohsmarked on'the net k of the instrument, the first makes a fifth withthe open chord, the second an octave, and so on for the rest, cor-responding with the intervals of the military trumpet.
Trumpet-Flower. See Bignonia.
TRUNCATED, in general, is an appellation given to suchthings as have, or seem to have, their points cut off: thus we say,a truncated cone, pyramid, leaf, &c. In entomology it means whenthe elytra (of upper wings) arc shorter than the abdomen, andterminated bv a transverse line,
TRUNDLE is a carriage with low wheels, whereon heavy andcumbersome burdens are drawn.
TRUNK, in botany, that part of the herb which arises immedi-ately from the root, and is terminated by fructification ; the leaves,buds, and auxiliary parts of the herb not entering into its descrip-tion. See Botany .
TRUNNIONS, [trognons, Fr.] the knobs or bunches of agun that bear it on the cheeks of a carriage.
TRURO, a borough of England, in Cornwall , at the mouth ofthe Fade. 11 miles N. N. E. of Falmouth , 79 W. by S. of Ex-eter and 257 VV. bv S. of London , Lon. 4, 55. VV. Lat. 42.l.N.
9 T
TRURO;