the return or progressive motion of a moving body, occasioned by some obstacle which hindered it from pursuing its former direction.

Circular Instrument of Reflection, an instrument for measuring angles to a very great degree of accuracy. It was invented by the celebrated astronomer Mr Tobias Mayer of Gottingen, principally with a view to do away the errors of the divisions of the limb; and has since been much improved by the Chevalier de Borda, and M. J. H. de Magellan. This instrument is particularly applicable to the measuring of the distances of the heavenly bodies, and was used by the French in their part of the operation for determining the difference of meridians of Paris and Greenwich. For the description, rectification, and use of this instrument, see the article Navigation, and Mackay on the Longitude, vol. i. p. 44.

Reflection of the Rays of Light, in catoptries, is their return, after approaching so near the surface of bodies as to be thereby repelled or driven backwards. For the causes of reflection, see Optics, Index at Rays of Light, and Reflection of Light, &c. For the application of the doctrine of reflection to mirrors, see Optics, p. 347—349. See also Mirror, Burning-Glass, and Glass-Grinding; and for the coating or polishing of mirrors, see the article Polishing of Looking-glasses, &c. See also Telescope.

Reflection is also used, figuratively, for an operation of the mind, whereby it turns its view backwards as it were upon itself, and makes itself and its own operations the object of its disquisition; and by contemplating the manner, order, and laws, which it observes in perceiving ideas, comparing them together, reasoning, &c., it frames new ideas of the relations discovered therein. See Metaphysics.