A Guide To The Scientific Knowledge Of Things Familiar Part 69

Q. _Why is the TEMPERATURE of ISLANDS more EQUABLE than that of CONTINENTS?_

A. Because the _water_ around the island _absorbs_ the extreme heat of summer, and _gives out_ heat to mitigate the extreme cold of winter.

Q. _Why does the sea round an island GIVE OUT heat in winter?_

A. Unless the _sea be frozen_ (which is rarely the case), it is _warmer_ than the frozen land; and, therefore, the warmth of the sea air (mixing with the cold land air) helps to mitigate the intense cold.

Q. _Why are there WAVES in the sea?_

A. The wind (acting on the surface of the sea) _piles up ridges of water_, which leave behind an _indentation_: as the water on all sides rushes to _fill up this indentation_, the disturbance spreads on all sides, and billow rolls after billow.

Q. _Why does WIND in England generally feel COLD?_

A. Because a _constantly changing surface_ comes in contact with our body, to draw off its heat.

Q. _Why is a ROOM (even without a fire) generally WARMER than the OPEN AIR?_

A. As the air in a room is _not subject to much change_, it soon becomes of the same temperature as our skin, and no longer feels cold.

Q. _Why do we generally feel COLDER out-of-doors?_

A. Because the air (which surrounds us) _is always changing_; and as fast as _one_ portion of air has become warmer by contact with our body, _another colder portion_ surrounds us to absorb more heat.

Q. _Why are HOT FOODS made COOL by BLOWING them?_

A. Blowing causes the air (which covers the hot food) _to change more rapidly_; in consequence of which, the hot air is _quickly blown away_, and gives place to fresh _cold air_.

Q. _Why do ladies FAN THEMSELVES in hot weather?_

A. By the action of the fan, _fresh particles of air_ are perpetually brought in contact with the face, and every fresh particle of air _absorbs some heat_ from the skin.

Q. _Does the fan COOL the AIR?_

A. No; it makes the _air hotter_, by imparting to it the heat _out of our face_: but it cools the _face_ blown upon, by transferring its heat to the _air_.

Q. _Is the AIR in SUMMER time ever so hot as our bodies?_

A. No, not in England. In the hottest day in summer, the air of England is 15 or 20 degrees cooler than the human body.

Q. _How fast does wind travel?_

A. A gentle breeze goes at about the rate of 5 miles an hour. A high wind from 20 to 60. A hurricane from 80 to 100 miles an hour.

Q. _How is the VELOCITY of WINDS ascertained?_

A. By observing the velocity of the clouds, and by an instrument for the purpose.

This instrument is called an ANEMOMETER.

Q. _How is the VELOCITY of the CLOUDS ascertained?_

A. By observing the speed of their shadow along the ground; which is found in a high wind to vary from 20 to 60 miles an hour.

Q. _Why is there always a strong DRAUGHT through the KEYHOLE of a door?_

A. As the air of the room we occupy is _warmer than the air in the hall_, therefore the cold hall air _rushes through the keyhole_ into the room, and causes a draught.

Q. _Why is there always a strong DRAUGHT UNDER the DOOR, and through the crevice on each side?_

A. The cold air _rushes from the hall_ under the door, &c. into the room, to supply the _void_ caused in the room (by the escape of warm air up the chimney, &c.)

Q. _Why is there always a DRAUGHT through the WINDOW crevices?_

A. The external air (being colder than the air of the room we occupy) rushes through the window crevices _to supply the deficiency_, caused by the escape of air up the chimney, &c.

Q. _Why is there more DRAUGHT if you open the LOWER SASH of a window, than if you open the UPPER sash?_

A. If the _lower_ sash be open, the _cold external air_ will rush more freely _into the room_; but if the _upper_ sash be open the _heated air of the room_ will _rush out_; and (of course) there will be less draught.

Q. _By which means is the ROOM better VENTILATED, by opening the lower or the upper sash?_

A. A room is better _ventilated_ by opening the _upper sash_; because the hot vitiated air (which always ascends towards the ceiling) _can better escape_.

Q. _By which means is a HOT ROOM more quickly COOLED--By opening the upper or the lower sash?_

A. A hot room is _cooled more quickly_ by opening the _lower sash_; because the cold air can enter more freely by an _under_ current, than by one _higher up_.