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 pale 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 plates 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 rings 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 diameters 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 the glasses, where the rings are success sively made, by the limits of the seven 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, sal, la, mi, th, that is, as the, cube roots of the squares of the numbers 1, 4, 1, s These rings 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 medidm 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 the microscope must con tinually perceive. See NEWTOX'S OeTics : see also Cotoun, MOT, rout, and unlanful 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, th ough they shall after depart of their own accord without doing any thing, this is an unlawful as sembly. By 34 Edward III. c. 1, it is enact ed, that if a justice find persons riotously assembled, he alone has not only power to arrest the offenders, and bind them to their good behaviour, or imprison them if they do not offer good bail ; but he may also authorize others to arrest them, by a bare verbal command, with out other warrant ; and by force thereof, the persons so commanded may pursue and arrest the offenders in his absence, as well as presence. It is also said, that after any riot is over, any one justice may send his warrant to arrest any person who was concerned in it, and that he may send him to gaol till he shall find sureties for behaviour. The punishment:of unlawful assemblies, if to the number of twelve, may be capital, according to the circumstances which at tend them ; but from the number of three to eleven, it is by fine and imprisonment only. The same is the case in riots and routs by the common law, to which the pillory, in very enormous cases, has been sometimes superadded.
By the act 1 George II. st. 2, c. 5, every justice, mayor, sheriff; &c. shall, upon notice Of a riot, or unlawful, tumul tuous assembly of twelve persons, em ceed to the place, and make proclama tion for them to depart, upon the pains of that act commonly called the riot-act. If any person shall wilfully oppose or hurt any person going to make procla mation, and prevent the same, he shall be guilty of felony, without benefit of clergy. If twelve continue together af ter proclamation, for one hour, it is felo .
ny, in like manner. And every justice, &c. shall apprehend persons, and if the rioters are killed, the justice, &c. shall hot answer for it. A riot, though of fewer persons than twelve, to destroy any ohurch, chapel, meeting, or dwelling house, out-house, &c. is a capital felony: and the hundred shall answer the da mages, as in case of robbery.
If two justices go out to quell a riot, they may assemble the posse comitatus, and every person capable of travelling is, apon being warned, to join them, on pain of imprisonment. 13 Henry IV. c. 7, s. 1, 2, 11, 5. c. 8, s. 2.