513. Why does the quicksilver reflect the rays of light?
Because, being densely opaque to light, and presenting also a bright surface, it is a good reflector, and it throws back the whole of the rays.
514. What has the glass to do with the reflection?
The glass has nothing to do with the reflection, except that it affords a field upon which the reflecting surface of the quicksilver is spread; and it keeps the air and dirt from dulling the quicksilver.
The parts of a mirror from which the quicksilver is rubbed away give no reflection that could assist the reflecting power of the quicksilver. That the surface of the glass does not reflect the image, is shown by the fact, that if you put the point of any object against the glass, the thickness between the point and the place where the reflection of it begins, will show the exact thickness of the glass.
515. Why does a compound mirror (a multiplying mirror) exhibit a large number of images of one object.
Because all objects reflect rays of light in every direction, and therefore the different mirrors, being at various angles, receive each a reflection of the same object.
516. Why does a window-pane appear to be a better reflector by candle-light than by day-light?
The reflecting power of glass is precisely the same by night as by day, and is always very feeble. But it appears to be greater by night, because the surrounding darkness increases the apparent strength of the reflection.