R E F 



Tor the refining of other matters, aa camphor, cinnabar, 

 fulphur, fait, borax, &c. fee Camphou, Cinnabar, Sul- 

 phur, Salt, &c. 



REFIRTH VoE, in Geography, a bay oh the E. coall 

 of the inand of Yell. N. lat. 60° $8'. W. long. 1° 25'. 



REFITTING, in Sea Language, denotes the repairing 

 of any damages which a fhip may have fullained in her fails 

 and rigging, by battle or tempeiluous -iVeather. 



REFLECTED Rav. See Ray. 



Reflected Fifion. See Reflex and Vlsion. 



REFLECTING, or Reflective Dial, is a fort of 



R E F 



their progrela without deviating from thofe planes in which 

 their former paths lay, and which are perpendicular to 

 the furface of the mediums, but they no longer retain 

 the fame direction, a part of them, and fometimcs nearly 

 tile whole, being reflefted back from the furface, while the 

 remaining part is tranfmitted and refraftcd, or bent. No 

 inilance occurs of the abrupt change of the denllty of 

 a medium, without a partial refleftion of the light paffing 

 either into the denfer, or into tlie rarer medium ; and the 

 more obliquely the light falls on the furface, the greater, in 

 general, is the refiedled portion. No body is fo black as 



dial, which fhews the hour by means of a thin piece of to reflect no light at all, and to be perfeftlv invifihl 



looking-ghfs plate, duly placed to call the fun's rays to the 

 top of a ceiling, on which the hour-lines are drawn. 

 Reflecting Micro/cope. See Microscope. 

 Reflegtinc Level. See Level. 

 Reflecting Tele/cope. See Telescope. 

 REFLECTION, or Reflexion, in Mechan'r.s, the re- 

 turn, or regredive motion of a moveable, occafioned by 

 the refiftance of a body, which hindered its purfuiiig its 



lormer airection. ^ „ ^^ .^^ g^^^^ v,,\|j»jicli lu luc du. ivieiais, m ge- 



lt is controverted whether there be any moment's reft or neral, rcfledt a great proportion of the light falling on them • 

 interval between the incidence and the refledlion. For the and even the reflection from the common furface of glafs and 

 affirmative ftand the Peripatetics, and all who conceive the mercury appears to be but little weaker than the refleftion 

 reflefted motion to be different from the incident one of the from the furface of mercury immediately expofed to the air 

 fame body. The motion of incidence, according to thefe fo that the optical denfity of tiie metals muft be exceeding-ly 



ilrong light ; although at the furface fepar'ating two very 

 rare bodies, as two kinds of gas, the refleftion is too faint to 

 be perceptible ; but in this cafe the feparation is feldora 

 perfectly abrupt. The quantity of light reflefted, when 

 other circumltances are equal, appears to be always greateft 

 when the difference of the optical or refraftive denfity of the 

 two fubltances is the greateft. Thus, the refleftion from 

 the common furface of glafs and water is much weaker than 

 from a furface of glafs expofed to the air. Metals, in 



authors, is wholly loll, and deltroyed, by the refiftance of 

 the obflacle ftruck againft ; and the moveable is thus ren- 

 dered abfolutely quiefcent in the point of contaft, till a 

 new motion of refleftion is produced in it, from a contrary 

 caufe. 



The Cartefians afTert the negative ; abfolutely denying any 

 reft at all between the incidence and refleftion : urging, that 

 if the motion were once deftroyed, though but for a moment, 

 there would be nothing to excite it again ; but the body 

 would perfevere in that new flate, as much as if it had 

 been at reft a thoufand years. 



Accordingly Rohault, and others, define refleftion to 

 be no other than a change of determination ; or a continua- 

 tion of the former motion in a new direftion. 



As, fay they, a pendulum, when arrived at its greateft 

 fweep, does not itop ; fo a hard body, by ftriking on another 

 hard one, does not reft, but purfues its motion the con- 

 trary way, according to the eftablifhed law of nature ; 

 and this from the immediate influence or impulfe of the 

 caufe that firft moved it. But this doftrine is now generally 

 fet afide. 



Refleftion is conceived, by the lateft and beft authors, as 

 a motion peculiar to elaftic bodies, whereby, after ftriking 

 on others which they cannot remove, they recede, or turn 

 back by their elaftic power 



great. It appears, alfo,' that a portion of the light fallfng 

 on a reflefting furface, is always tranfmitted to a certain 

 depth, notwitliftanding the apparent opacity of any large 

 maffes of the fubftance. Thus, if we cover a fmall hole of 

 a window-fliutter witli the tliinneft leaf-gold, we fhall find 

 that it tranlmits a greenifli light, which muft have paffed the 

 reflefting furface, but which, if the gold had been but one 

 ten-thoufandth of an inch in thicknefs, would have been 

 wholly interrupted, and probably in the fame manner as by 

 pairing through 700 feet of water. See Light and Re- 

 fraction. 



The refleftion of the rays of light from' the furfaces of 

 bodies, is the means by which bodies become vifible. 



And the difpofition of bodies torefleft this or that kind 

 of rays moft copioufly, is the caufe of their being of this or 

 that colour. 



The refleftion of hght from the furfaces of mirrors, 

 makes the fubjeft of catoptrics ; which fee. See alfo 

 Mirror. 



The refleftion of light, fir Ifaac Newton has fhewn, is 

 not eftefted by the rays ftriking on the very parts of the bo- 

 dies ; but by fome power of the body equally diffufed 

 throughout its whole furface, by which it afts upon the ray, 

 attrafting or impelling it witiiout any immediate contaft. 

 This power he fhews to be the fame, by which, in other 



On this principle, it is all'erted, that there may be, and circumltances, the rays are refrafted ; and by which they 

 is, a period of reft between the incidence and the refle(?lion ; are at firft emitted from the lucid body. See Refraction 



lince the reflefted motion is not a continuation of the other, 

 but a new motion, arifing from a new caufe or principle, 

 viz. the power of elafticity. 



it is one of the great laws of refleftion, that the angle a 

 reflefted body makes with the plane of a reflefting obftaclc, 

 is equal to that in which it ftruck on that oljftacle. For 

 the feveral laws of motion obferved in the refleftions of bo- 

 dies, fee Percussion 



The arguments he produces to prove this are as follow : 

 I. Becaufe the furfaces of poliflied glaffes, which to the 

 eye appear imooth, are yet, in reality, very rugged and 

 uneven .(pohihing being nothing but the grating, fcratching, 

 and breaking off the coarfer protuberances, by means of 

 fand, glafs, putty, tripoli). If the rays of light, there- 

 fore, were reflefted by ftriking on the folid parts of the 

 glafs, the refleftions would never be fo accurate as we find 



Reflection of the ra^s of light, in Optics, is amotion of they are, but the rays would even be as much fcattered by 



the rays, by which, after impinging on the folid parts of bo- the moft polifhed glafs, as by the rougheft. It remains, 



dies, or rather, after a very near approach to them, they therefore, a problem how glafs, poHfhcd by frettino- fub- 



recede, or are driven from them. ftances, can refleft light fo regularly as it does ; which pro- 



When rays of light arrive at a furface, which is the blem is fcarcely otherwife to be folvcd, than by faying, that 



boundary of two mediums not homogeneous, they continue the refleftion of a ray is effefted, not by a fingle point of the 



12 reflecting 



