Q. _When we plunge our HANDS into a basin of WATER, why does it produce a sensation of COLD?_ A. Though the water (in which we wash) _is really warmer_ than the air of our bed-room; yet because it is a _better conductor_, it _feels colder_. Q. _Why does the CONDUCTING power of water make it feel COLDER than the air, though in reality it is WARMER?_ A. Because _it abstracts heat from our hands so rapidly_, that we feel its loss; but the air abstracts heat _so very slowly_, that its _gradual loss is hardly perceptible_. Q. _Is water a GOOD CONDUCTOR of heat?_ A. No; _no liquid is a good conductor_ of heat; but yet water is a _much better conductor than air_. Q. _Why is WATER a BETTER CONDUCTOR of heat than AIR?_ A. Because _it is less subtile_; and the conducting power of any substance depends upon _its solidity_, or the _closeness of its particles_. Q. _How do you know that WATER is NOT a GOOD CONDUCTOR of heat?_ A. Because water may be made to _boil at its surface_, without imparting sufficient heat to _melt ice a quarter of an inch below the boiling surface_. Q. _Why are NOT LIQUIDS GOOD CONDUCTORS of heat?_ A. Because the heat (which should be transmitted) _produces evaporation_, and _flies off in the vapour_. Q. _Why does a POKER (resting on the fender) feel so much COLDER than the HEARTH-RUG, which is further off the fire?_ A. The poker (being an excellent conductor) _draws heat from the hand much more quickly than the rug_, which is a bad conductor: and, therefore, (though both are _equally warm_) the poker seems to be much colder. Q. _Why are HOT BRICKS (wrapped in cloth) employed in cold weather to KEEP the FEET WARM?_ A. Bricks are _bad conductors_ of heat, and cloth or flannel _still worse_: therefore a hot brick (wrapped in flannel) will _retain its heat a very long time_. Q. _Why is a TIN PAN (filled with HOT WATER) employed as a FOOT WARMER?_ A. Because _polished tin_ (being a bad radiator of heat) _keeps hot a very long time_; and warms the feet resting upon it. Q. _What is meant by being a "bad RADIATOR of heat?"_ A. To radiate heat is to _throw off heat by rays_, as the sun; a polished tin pan does _not throw off the heat of boiling water_ from its surface, but _keeps it in_. Q. _Why is the TIN FOOT-WARMER covered with FLANNEL?_ A. 1st--To prevent the perspiration of the foot from taking off the _polish_ of the tin: 2ndly--Flannel is a _very bad conductor_; and, therefore, helps to keep the tin hot _longer_: and 3rdly--If the feet were _not protected_, the conducting surface of the tin _would feel painfully hot_. Q. _What harm would it be if the POLISH of the tin were injured by the perspiration of our feet?_ A. _Polished_ tin throws off its heat _very slowly_; but dull, scratched, painted, or dirty tin, _throws off its heat very quickly_: if, therefore, the tin foot-warmer were to _lose its polish_, it would _get cold in a much shorter time_.