The Reason Why. Robert Kemp Philp
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Air, is that sent from the lungs light or heavy, 14
Air, is it a good or bad conductor of heat, 150
Air, why is a still summer said to be sultry, 171
Air, why does it feel cooler when in motion, than when still, 175
LESSON II.
Air, when is it hot enough to destroy life, 179
Air, why is it often excessively hot in chalk districts, 219
Air, is it heated directly by the sun's rays, 221
Air, why does it ascend the chimney, 240
Air, why does it fly through the doors and windows towards the fire-place, 241
Air, what does the motion of it in our rooms illustrate, 242
Air, why does it become charged with watery vapour, 346
Air, when is it said to be saturated with vapour, 430
Air, what proportion of water is air capable of holding in the form of vapour, 431
Air, what is its weight relative to that of water, 647
LESSON III.
Air, which is heavier, dry or vaporised, 697
Air-pistol (or pop-gun), why does pressure applied to the handle propel the cork, 854
Air-pistol, why must the handle be drawn out before the cork is placed in, 855
Air, why does fresh impart a healthy appearance, 915
Albumen, what is it, 899
Alkalies, what are they, 36
Amber, or electrum, what is it, 564
Animals, how is their greater warmth in winter provided for, 168
Animal forms, why are there so many, 1029
Animal furs, why do they become thicker in the winter, 1035
Animals, why have carnivorous, long pointed teeth, 1038
LESSON IV.
Animals with long necks, why have they large throats, 1049
Animals, why cannot flesh-eaters live upon vegetables, 1071
Animals, why can ruminating recover the food from their paunches, 1089
Animals, why can ruminating keep the chewed from the unchewed food in their stomachs, 1090
Animals, why do the smaller animals breed more abundantly than the larger ones, 1094
Animals, domestic, why may change of weather be expected when they are restless, 1107
Animals, plants, and minerals, what are the differences between them, 1140
Animals that graze, why do they crop the tender blades, but leave the tall grass, 1287
LESSON V.
Animals, distribution of, 1326
Arms and hands, why do we see blue marks upon them, 896
Arms and legs, why does it require the influence of the will to set them in motion, 917
Arms and legs, why are they made subject to the will, 919
Ascending, what is the cause of bodies, 775
Atmosphere, how is it heated, 232
Atmospheric humidity, why does it sometimes form clouds, at others form dews, fogs, mists, &c., 409
Atmospheric pressure, how high will it raise water, 652
Atmosphere, what is the, 639
Atmosphere, to what height does it extend, 639
Atmosphere, what is the amount of its pressure, 641
Atmosphere, what is the proportion of watery vapour in the, 642
Atmosphere, why are its upper regions intensely cold, 444
Atmosphere, what is the greatest height ever reached in the, 648
LESSON VI.
Atmospheric pressure, what is the total amount on the earth's surface, 644
Atmosphere, what is the amount of its pressure upon the human body, 645
Atmosphere, why do we not feel its pressure, 646
Atmosphere, to what extent may its pressure vary, 702
Attractive agent, what is an, 76
Attraction, what is it, 772
Attraction, how many kinds are there, 773
Aurora Borealis, what is the cause of, 590
Bananas or plantains, where are they cultivated, 1220
Bark Peruvian, where is it produced, 1228
Barometer, what is a, 691
Barometer, why does it indicate the pressure of the atmosphere, 692
Barometer, why is it also called a "weather-glass", 693
Barometers, why are they constructed with circular dials, 694
Barometer, why does the hand change its position when the mercury rises or falls, 695
Barometer, why does tapping its face cause the hand to move, 696
Barometer, why does its fall denote the approach of rain, 699
LESSON VII.
Barometer, why does its rise denote the approach of fine weather, 700
Barometer, how does it enable us to calculate the height of the mountains, 701
Barometer, when does it stand highest, 704
Barometer, when does it stand lowest, 705
Barometer, what effect has heat upon the, 707
Barometer, what effect has cold upon the, 708
Balloons, why do they ascend in air, 830
Balloons, why do air balloons become inflated, 831
Balloons, why do they sometimes burst when they reach a high altitude,