A. Because if any thing _sucks in heat_ like a sponge, it cannot _throw it off_ from its surface; and if any thing _throws off heat_ from its surface, it cannot _drink it in_. Q. _Why are REFLECTORS always made of LIGHT-COLOURED and highly POLISHED METAL?_ A. Because _light_ coloured and _highly polished metal_ makes the best of all reflectors. Q. _Why do not PLATE-WARMERS BLISTER and scorch the WOOD behind?_ A. Because the bright tin front _throws the heat of the fire back again_, and will not allow it to penetrate to the wood behind. Q. _If metal be such an excellent CONDUCTOR of heat, how can it REFLECT heat, or throw it off?_ A. Polished metal is a _conductor of heat_, only when _that heat is communicated by actual contact_; but whenever heat _falls upon bright metal in rays_, it is _reflected back again_, and the metal remains _quite cool_. Q. _What is meant by "heat falling upon metal IN RAYS," and not "by contact"?_ A. If a piece of tin were thrust _into_ a fire, it would be _in actual contact with the fire_; but if it be _held before a fire_, the heat of the fire _falls upon it in rays_. Q. _What is the use of the TIN SCREEN or REFLECTOR used in ROASTING?_ A. The tin reflector _throws the heat of the fire back upon the meat_; and, therefore, assists the _process of roasting_ and helps _to keep the kitchen cool_. Q. _How does a tin REFLECTOR tend to keep the KITCHEN COOL?_ A. Because it _confines the heat to the hearth_, and prevents it from being dispersed throughout the kitchen. Q. _Why does a LAMP GLASS DIMINISH the SMOKE of a LAMP?_ A. As _glass is a reflector_, it reflects the heat of the lamp _back upon the flame_; in consequence of which, _less carbon escapes unconsumed_ (as smoke). Q. _Why are SHOES HOTTER for being DUSTY?_ A. 1st--Because dust absorbs heat: and 2ndly--As it destroys the _blackness of our shoes_, it prevents them from _throwing off the heat of our feet in rays_. Q. _Why can we not SEE into the ROAD or STREET, when a CANDLE is lighted in a room?_ A. _Glass is a reflector_; and, therefore, throws the rays of the candle _back into the room_, and thus prevents our seeing into the road or street. Q. _Why can persons in the DARK STREET see into a ROOM (lighted by a candle or lamp)?_ A. The pupil of the eye _expands greatly_, when persons are in the dark; and, therefore, when any one in the dark street looks into a light room, _his dilated pupil_ sees every thing distinctly. Q. _Why does it always FREEZE on the TOP of a MOUNTAIN?_ A. Air is heated _by the reflection of the earth_, and not by the rays of the sun; and, as there is no earth round a mountain-top _to reflect heat_, therefore, it remains intensely cold. CHAPTER XVI. 4.--RADIATION. Q. _What is meant by RADIATION?_ A. Radiation means _the emission of rays_: thus the sun radiates both light and heat; that is, it emits _rays of light and heat_ in all directions. Q. _When is heat RADIATED from one body to another?_