in physics, a quality in certain bodies, whereby they give paffage to the rays of light: in contradiftinction to opacity, or that quality of bodies which renders them impervious to the rays of li-ht.

It has been generally fuppofed by philofophers, that tran- sparent bodies have their pores difpofed in straight lines, by which means the rays of light have an opportunity of pene- trating them in all directions; but fome experiments in electricity have made it apparent, that by the action of this fluid the moft opaque bodies, fuch as fulphur, pitch, and fealing-wax, may be rendered tranfparent as glafs, while yet we cannot fuppofe the direction of their pores to be any- way altered from what it originally was (fee Electricity, n°4.) A curious inftance of an increafe of transparency we have in rubbing a piece of white paper over one that has been written upon or printed; while the white paper is at reft, the writing or print will perhaps scarce appear through it; but when in motion, will be very eafily legible, and continue fo till the motion is difcontinued.