RIN 



tracted itself breadthwise, to form a kind 

 of ring round a new circle that arose 

 near its middle. The pressure having 

 been carried to a certain term, Newton 

 stopped, and observed as follows. At 

 the point of contact was a black spot that 

 was encompassed by several series of co- 

 lours. The order of the colours from the 

 centre to the borders of the two glasses 

 was this : in the first series, blue, white, 

 yellow, and red ; in the second, violet, 

 blue, green, yellow, and red ; in the 

 third, purple, blue, green, yellow, and 

 red; in the fourth, green and red; in the 

 fifth, greenish blue and red ; in the sixth, 

 greenish blue, and pule red ; in the se- 

 venth, greenish blue, and reddish white. 

 Beyond this number, the tints of which 

 were regularly paler, the colour became 

 white. Newton measured the diameters 

 of the annular bands, formed of these dif- 

 ferent colours, by taking the points where 

 they had most lustre ; and he found that 

 the squares of those diameters were to 

 one another as the terms of the ascending 

 progression, 1, 3, 5, 7, 9, 11, &c. ; from 

 which it results, that the intervals be- 

 tween the two glasses, relatively to the 

 corresponding points, followed the same 

 progression. From these proportions, it 

 was merely necessary to ascertain the ab- 

 solute length of a single diameter, to 

 know the lengths of all the others, as 

 well as the different thickness of the 

 platqs of air at the points where the dif- 

 ferent colours were seen. He drew up a 

 table of these degrees of thickness, by 

 which it appears, that the most intense 

 blue, for example, that of the first series, 

 is expressed by a thickness of 0.000024 of 

 an inch, supposing the visual ray to be 

 nearly perpendicular to the two glasses. 

 Sir Isaac Newton having measured also 

 the diameters of the inngs at the inter- 

 mediate places where the colours were 

 obscure, found that their squares were 

 to one another as the even numbers 2, 4, 

 6, 8, 10, 12, &c. ; and hence the intervals 

 between the glasses, at the correspond- 

 ing points, observed a similar progres- 

 sion. The diameter's of the rings increas- 

 ed or diminished, as the visual ray was 

 more or less inclined to the surface of the 

 two glasses, so that the greatest contrac- 

 tion took place when the eye was situated 

 perpendicularly above the glasses. The 

 diameters also retained the same propor- 

 tions to one another. 



From other curious observations on 

 these rings, made by different kinds of 

 light thrown upon them, he inferred, 

 that the thicknesses of the air between 



RIO 



the glasses, where the rings are succe 

 sively made, by the limits of the seve 

 colours, red, orange, yellow, green, blue, 

 indigo, and violet, in order, are one to 

 another as the cube roots of the squares 

 of the eight lengths of a chord, which 

 sound the notes in an octave, sol, la, fa, 

 sol, la, mi, fa, sol; that is, as the cube 

 roots of the squares of the numbers 1, 

 f e ' I' I > I' I, IT These rin s Appeared 

 of that prismatic colour, with which they 

 were illuminated, and by projecting the 

 prismatic colours immediately upon the 

 glasses, he found that the light, which 

 fell on the dark spaces between the co- 

 loured rings, was transmitted through 

 the glasses without any change of colour. 

 From this circumstance he thought that 

 the origin of these rings is manifest; be- 

 cause the air between the glasses is dis- 

 posed according to its various thickness, 

 in some places to reflect, and in others to 

 transmit the light of any particular co- 

 lour, and in the same place to reflect that 

 of one colour, where it transmits that of 

 another. 



In examining the phenomena of co- 

 lours made by a denser medium sur- 

 rounded by a rarer, such as those which 

 appear in plates of Muscovy glass, bub- 

 bles of soap and water, &c, the colours 

 were found to be much more vivid than 

 the others, which were made with a rarer 

 medium surrounded by a denser. From 

 the preceding phenomena it is an ob- 

 vious deduction, that the transparent 

 parts of bodies, according to their several 

 series, reflect rays of one colour and 

 transmit those of another ; on the same 

 account that thin plates, or bubbles, re- 

 flect or transmit those rays ; and this Sir 

 Isaac Newton supposed to be the reason 

 of all their colours. Another inference 

 is, that the particles even of those bodies 

 which we call opaque, are in reality trans- 

 parent, which persons who are in the 

 habit of using the microscope must con- 

 tinually perceive. See NEWTON'S Oi> 

 TJCS : see also Cotouu, &c. 



RIOT, rout, and imlawfid assembly. 

 When three persons, or more, assemble 

 themselves together, with an intent mu- 

 tually to assist one another, against any 

 who shall oppose them in the execution 

 of some enterprise of a private nature, 

 with force or violence, against the peace, 

 or to the manifest terror of the people, 

 whether the act intended were of itself 

 lawful or unlawful, if they only meet for 

 such a purpose or intent, though they shall 

 after depart of their own accord without 





