more turned out of their course, in passing from one medium to another; it follows, that after such refraction they will be separated, and their distinct colour observed. Of these, the most refrangible are violet, and the least red; and the intermediate ones, in order, are indigo, blue, green, yellow, and orange. This separation is very entertaining, and will be observed with pleasure in holding a prism in the beams of the sun.
As all these rays differ in refrangibility, so they do in reflexibility; that is, in the property of being more easily reflected from certain bodies than from others; and hence arise, as hath been said, all the colours of bodies; which are, in a manner, infinite, as an infinite number of compositions and proportions, of the original colours, may be imagined.
The whiteness of the sun's light is compounded of all the original colours, mixed in a due proportion.
Whiteness, in bodies, is but a disposition to reflect all colours of light, nearly in the proportion they are mixed in the original rays; as, on the contrary, blackness is only a disposition to absorb or stifle, without reflection, most of the rays of every sort that fall on the bodies.
Light is successively propagated with an almost inconceivable swiftness; for it comes from the sun, to this our earth, in about seven or eight minutes of time, which distance is about 80,000,000 English miles.
Besides colour, we are supposed to see figure; but, in truth, that which we perceive when we see figure, as perceivable by sight, is nothing but the termination of colour.
OF HEARING.
Next to seeing, hearing is the most extensive of our senses. The ear is the organ of hearing, whose curious structure is to be learnt from anatomy.
