Page:St. Nicholas, vol. 40.1 (1912-1913).djvu/111

1912.]

Practically all common objects, except metals, with which we come in contact are non-conductors of heat, that is, heat will not flow through them readily. Such objects are wood, paper, cloth, etc.; but metal objects, generally speaking, conduct heat readily. All objects, including the two classes just mentioned, are, as a rule, at a lower temperature, or colder, than our bodies; hence, when we touch an object, as wood, which will not conduct heat readily, no heat flows from the hand into the object, and it does not give us the impression of being cold; but when the warm hand comes in contact with an object which is a good conductor of heat, such as metal, heat flows from the hand into the object, tending to warm it to the same temperature as the body. This loss of heat on the part of the hand gives us a sensation of coldness. Of course, if the object has been placed in the sun or any hot place where it has acquired a temperature above that of the body, the phenomenon is reversed, in that the metal gives its heat rapidly to the hand, while the wood, being a poor conductor of heat, does not; consequently, the metal feels warmer than the wood under such conditions.—, State Normal College, Ypsilanti, Michigan.

It is interesting to notice that the hand, which is exceedingly sensitive to differences of touch, is not as sensitive to heat and cold as the face, so that when you try the cold feeling of metals, it is best to apply them to your cheek or nose.

Some things besides metals feel cold, as you will find if you step with bare feet on a cold winter morning upon a piece of oil-cloth instead of upon the carpet. This also is caused by its power of conducting heat.

Different metals vary in their heat conductivity, silver and copper being the best conductors, and alloys, such as brass, German silver, and so on, being much poorer ones. If you put solid silver spoons and plated spoons into a cup of hot water together, you will find that the heat goes much faster up the handles of the solid spoons than up those of the plated ones.

An expert will distinguish between a ball of quartz crystal and a similar ball of glass by touching his tongue to both, because the tongue is very sensitive to cold, and the quartz, as it conducts heat more rapidly, feels much colder.—, Yale University.

It is a very clever cat, indeed, that can sit on its hind feet and wash its face with both paws at once! I do not imagine it has any significance beyond that. A cat can be taught to sit up and beg, and from that point I suppose this other feat would be only a step. Possibly this cat bears the same relation to the rest of her tribe as the man who must do things in double-quick time bears to his fellow-men.