Page:Cyclopaedia, Chambers - Supplement, Volume 2.djvu/360

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yet radically diffolved by any experiment, whatever fome may have imagined. Even fome earths will turn into metals by the admixture, and intimate union of a phlo- gifton, or inflammable principle; but thefe metals never need any fuch principle to aflift their reduclion. Ibid. p. 186. REDUNDANT {CycL) — Redundant interval, in mufic, is ufed for an interval exceeding the truth by a comma. See Interval.

Some apply redundant to an interval exceeding a diatonic interval by a femitone minor j but this is more ufually called a fupcrfluous interval. See thearticles Second, CycL and, Interval, Suppl. REDUVIA, in medicine, a word ufed by fome for a whit- low, and by others for a painful crack, or other diforder about the nails, either of the fingers or toes. REED, arundo, in botany. See Arundo, Reed, calamus, Kkewife denotes a fort of meafure, otherwife

called canna. See Canna. Reed fparrow, the Englifli name of a bird by many efteemed of the picas, or wood-pecker kind, having fhort legs, and climbing up reeds, ckc. as the other upon trees ; but it wants the great character of that genus of birds, having its toes placed only one behind, and three before, as in the genera iity ot other birds. There are two fpecies of this bird, ; greater and a Icfler ; the hrft called by authors junco, and eincluff and the other cannevarola, and by fome pajfer arun- dinaceus minor. Ray's Ornitholog. p. 99. See the articles Junco and Cannevarola. REEN mojfa, a name ufed by fome for the mountain coral

loides, or rein deer mofs. REEVE (CycL) — Reeve, in zoology, the name of a bird which is the female of the avis pugnsx ; the male of which, from his long feathers round his neck, is called the ruffe. REFLECTING tele/cope (CycL)— See Telescope. REFLEX leaf, among hotanifts. See Leaf. REFLEXION (CycL)-~Cauflic by Reflexion. Rays of light being fuppofed to^ikie from a given point, and to be re- flecled by a given curve, fo as to make the angle of re- flexion equal to the angle of incidence ; a curve that touche: all the reflected rays is called the caiiflic by reflexion.

Thus, let S be the given point from whence the rays iflue, SL any incident ray. P L p the tangent at L. L C the radius of curva- ture at L, L m the reflecled ray conftituting the angli C L m, equal to C L S then if the reflected rays al ways touch the curve hme it is the cauftic by refle- xion.

Again, let S P, perpendicular to the tangent LP, meet it always in P, a point of the curve DP; let HME be the curve, by the evolution of which D P is described, and let P M touch HME in M ; join S M, and produce it to m, fo that S/a be equal to 2 S M : then will m be a point in the cauftic of the curve £ L, when S is the radiating point.

Hence, if perpendiculars be always drawn from the radiat- ing point to the tangents of the reflecling curve, and a new curve be fuppofed to be the locus of the inter feci ions of the perpendiculars and tangents, then will the evoluta of that new curve be fimilar, and fimilarly fituated to the cauftic by reflexion of the propofed reflecling curve. See Mac Lanrin's Fluxions, Art. 409.

The point ?n may be thus found. Let C R be perpendi cular to L R, the reflated ray, and let L s — L S ; then if L R be bifecced in ? , q m will be a third proportional to q s and q R jjhat is, q s : q R : : q R : q m> G r s q x q m = q R 1 — q L\ Id. Art. 410.

Mr. de YHopital, in his Analyfe des Inf. Petits, Se£l. 6. has treated of cauftics by reflexion.

D^V-f^i?* 10 ^ in g eometr y- See Point of reflexion.

REFRACTED (l>/.)-Refracted angle, in "optics, the angle contained between the refracled ray and the per- pendicular.

REFRACTION (<V.)-Refraction to the perpendicular, in optics, is when a ray fells from a lefs denfe into a more denfe medium, and fo approaches nearer the perpendicular.

Refraction from the perpendicular, in optics, is when a ra felling inclined -from a more denfe medium into one lefs denfe, in breaking departs further from the perpendicular.

CauJIics by Refraction. When rays of light, iffuing from a given point, are refracled at any curve, fo that the fine ot the angle contained by the refracled ray, and the per- pendicular to the curve, is always to the fine of the angle contained by the incident ray, and that perpendicular, "in one conftaiit ratio, the curve that touches all the refracled rays, is called the cauftic by refraction. Let S be the radiating point, SL any incident ray on the curve BL/, LR the' rrfraBtd ray, C the center of the

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curvature at L, C I perpendicular on the incident ray in I, C R perpendicular to the refracled ray in R; join S C

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and I R ; let R Z, perpendicular to R I, meet C I in Z ; join L Z, meeting S C in Q_; and let Q_M, parallel to R. Z, meet the refracled ray L R in M j then will the point M be in the cauftic. See Mac Lanrin's Fluxions, Art. 413.

The point M may alfo be determined, by defcribing-a circle L I R C on the diameter L C, and by drawing V C paral- lel to S L ; then applying R C in this circle, fo that it may be to C I, in the given ratio of the fine of refraclion, to the fine of incidence, joining V R, that meets C I per- pendicular from C to the incident ray in Z, joining L Z that meets S C in Q_, and drawing Q_M parallel to V R. When L Z is parallel to S C, the refracled ray is the af- fymptot to the cauftic. lb. Art. 414. The Marquis de l'Hopital has treated of cariftics h refrac- tion, in his Anal, des Inf. Pet. Sect. 7.

REFRANGIBLE, whatever is capable of bein» refracted. See Refrangibility, CycL

REFRIGERATORY, (CycL) a term ufed for a veffel of cold water, through which the worm of the alembic panes in the common method of diftillation, by means of which the vapours are condenfed. It is alfo ufed for the bucket head of the common fmall alembic, containing water for the fame purpofe.

REFUTATION, refutatio, in rhetoric, that part of the an- fwer made to an opponent, which difproves what had been advanced by him. Vojf. Rhet. I. 5. p. 382.

Sf£5S?5£T£2 tartar - See tartars r^™™*,,.

REGERENDARIUS, among the Romans, an officer who fubfenbed and kept a rcgifter of all petitions prefentcd to the prefect. Pitifc. in voc.

REGESTOLA, in zoology, a name ufed by fome authors for the mattagefs, or larger butcher bird, a very fmall hawk, not exceeding the fize of a common thrufli, but very fierce and voracious. Aldrovand, de Avib. SeeJYlAT- tagess and Lanius.

REGIMEN, (CycL) in medicine, a regulation of diet, with intent to reftore, or to preferve health. In chemiftry, it iigmhes the due regulation of fire.

REGINA aurarum, in zoology, a name given by Nieremberg to a bird called by the Mexicans cezeaecauhtli. It has ob- tained its name from its being able to fly againft the itrongeft winds. It is of the bignefs of an eagle, and its whole body is of a blackifh purple, variegated with a browmm yellow, and a deep black. Its wings are varie- gated with black, yellow, and grey. Its legs are red. Its claws very ftrong and fbarp ; and its beak like that of the parrot. It has fome rugofe fkin on the forehead, and about the beak, and its tail is black above, and <*rey under- neath. It feeds on fnakes, rats, and other vermin, hut will alfo eat human dung. It flies very high. It is a na- tive of Mexico, and breeds in fprinn. Its feathers toe faid to be a remedy for many difcafes. But the truth of this ac- count is much to be doubted. Ray's Ornilholoo- n lai

REGION (Q,/0_Regio N s of J fea. As tt narJraHrts, in their delcriptions of the fubterranean parts of the «lobe, difttnguifti the earth into three regions of different depths, in which different temperatures are obferved ; fo in de- scribing the fea, they allow it two regions; the one extend- ing from the furface of the water, down fo low as the ravs of the fun can pierce, and extend their influence ; and the other, from the lowed bounds of that to the bottom. It is eafy to fee, that thefe regions rather regard quality than fpace, and that their boundaries are far from being' regu- lar, or equal m all places, and at all times. The places expofed to the hottett funlhine will have the larccft upper region ; thofe where the fun has leaft power, will have the fmalleft; and the fame part of the fea will have its upper region more or lefs deep, according to the feafon of the year. This upper region of the fea is always more 01 leis hot; the lower region, except in fome few particular places, is every where cold ; and the water, where the upper region is large, is always remarkably full and quia in the lower. Boyle of Cofmieal Qualities'

Subterranean Region. The earth is not only divided on its furface into regions and countries, but phiiofonhers, who have had occalion to difcourfe of its inner part-', hue Mi divided them into three difrinct regions, according to their different depths from -the furface. The temperature of the fubterranean parts of the globe is diftinguiftied scenrfe to' the divifion of thefe regions, but is not fo regliar and

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