Suppose our head to be at A, and our feet at B; then the shadow of our head will be seen at D, and the shadow of our feet at C. (_See last figure._) Q. _Why do WINDOWS seem to BLAZE at SUN-RISE and SUN-SET?_ A. Because glass is a good _reflector of light_; and the rays of the sun (striking against the window glass) _are reflected_, or thrown back. Q. _Why do NOT windows reflect the NOON-DAY rays also?_ A. They do, but the _reflection is not seen_. Q. _Why is the reflection of the RISING and SETTING sun seen in the window, and NOT that of the NOON-DAY sun?_ A. As the angle of _incidence_ always equals the _angle of reflection_, therefore the rays of the noon-day sun enter the glass _too perpendicularly_ for their reflection to be seen. [Illustration: Here AB represents a ray of the noon-day sun striking the window at B; its reflection will be at C: But DB (a ray of the rising or setting sun) will be reflected to E (the eye of the spectator).] Q. _Why can we not see the REFLECTION of the SUN in a WELL, during the day-time?_ A. Because the rays of the SUN _fall so obliquely_, that they _never reach the surface of the water_ at all, but strike against the brick sides. [Illustration: Let BDEC be the well, and DE the water. The ray AB strikes against the brick-work _inside_ the well; and The ray AC strikes against the brick-work _outside_ the well. None will ever touch the water DE.] Q. _Why do we see the MOON reflected in a WELL very OFTEN?_ A. As the rays of the MOON are not so _oblique_ as those of the sun, they will often reach the water. _(See next figure.)_ Q. _Why are the STARS REFLECTED in a WELL, although the SUN is NOT?_ A. As the rays of the STARS are not so _oblique_ as those of the sun, they will often reach the water. [Illustration: Here the moon's rays AB, AC, both strike the water DE, and are reflected by it.] Q. _In a sheet of water at noon, the sun appears to shine upon only ONE spot, and all the REST of the water seems DARK,--WHY is this?_ A. Because the rays (which fall at various degrees of obliquity on the water) are _reflected at similar angles_; but as only those which _meet the eye of the spectator_ are visible, all the sea will appear dark but _that one spot_. [Illustration: Here of the rays SA, SB, and SC, only the ray SC meets the eye of the spectator D. The spot C, therefore, will appear luminous to the spectator D, but no other spot of the water ABC.] Q. _At night the MOON seems to be reflected from only ONE SPOT of a lake of water, while all the REST seems DARK,--WHY is this?_ A. Because the rays (which fall at various degrees of obliquity on the lake) _are reflected at similar angles_; but as only those which _enter the eye of the spectator_ will be visible, all the water will appear dark _but that one spot. (See last figure.)_ Q. _Why are MORE STARS visible from a MOUNTAIN, than from a PLAIN?_