A. If a reflector be _spotted, dull, or scratched_, it will _absorb_ heat, instead of _reflecting_ it; and, therefore, would be of no use whatsoever as a _reflector_. Q. _Why does HOAR-FROST remain on TOMBSTONES, long after it has melted from the GRASS and GRAVEL-WALKS of a church-yard?_ A. Tomb-stones being _white_, will _not absorb heat_, like the darker grass and gravel; and, therefore, _the white tombstones_ (being so much colder) _retain the hoar-frost_ after it has melted from other things. Q. _If black absorbs heat, why have those who live in HOT climates BLACK SKINS, and not WHITE skins (which would not absorb heat at all)?_ A. Though the black skin of the negro _absorbs heat_ more plentifully than the _white skin of a European_, yet the _blackness_ prevents the sun from _blistering_ or _scorching it_. Q. _How is it known that the BLACK colour prevents the sun from either BLISTERING or SCORCHING the skin?_ A. If you put a _white glove_ on _one hand_, and a _black glove_ on _the other_ (when the sun is burning hot), the hand with the _white_ glove will be _scorched_, but _not the other_. Q. _Which hand will FEEL the HOTTER?_ A. The hand with the _black glove_ will _feel_ the _hotter_, but it will not be _scorched_ by the sun; whereas the hand with the _white glove_ (though much _cooler_) will be _severely scorched_. Q. _Why does the BLACK skin of a NEGRO NEVER SCORCH or BLISTER with the hot sun?_ A. Because the _black colour absorbs_ the heat,--conveys it _below the surface_ of the skin, and converts it to _sensible heat_ and _perspiration._ Q. _Why does the WHITE EUROPEAN SKIN BLISTER and SCORCH when exposed to the hot sun?_ A. Because the _white will not absorb_ the heat; and, therefore, the hot sun _rests on the surface of the skin_, and scorches it. Q. _Why has a NEGRO BLACK EYES?_ A. The black colour of a negro's eyes defends them from the strong light of the tropical sun. If a negro's eyes were not _black_, the sun would _scorch them_, and every negro would be blind. Q. _Why is WATER KEPT COOLER (in summer time) in a BRIGHT TIN POT, than in an EARTHEN one?_ A. Because bright metal will _not absorb_ the heat of the summer sun, like an _earthen_ vessel. Q. _Why is BOILING water KEPT HOT in a BRIGHT TIN VESSEL longer, than in an earthen one?_ A. Because bright tin will not suffer the heat of the boiling water _to escape in rays_, as an earthen vessel does. CHAPTER XV. 3.--REFLECTION OF HEAT. Q. _What is meant by REFLECTING HEAT?_ A. To reflect heat, is _to throw it back in rays_ from the surface of the reflecting body, towards the place from whence it came. Q. _What are the BEST REFLECTORS of heat?_ A. All _bright_ surfaces, and _light colours_. Q. _Are GOOD ABSORBERS of heat GOOD REFLECTORS also?_ A. No; those things _which absorb heat best, reflect_ heat _worst_; and those _which reflect heat worst, absorb_ it _best_. Q. _Why are those things which ABSORB HEAT unable to REFLECT it?_