INDEX. 



321 



Seeing, sense of, how exerted, 241 iBounds, when flat, 121 



Senses, number of, 3 why seem louder in a church than 



what are th'jy, 3 in a plain, 128 



Sewers, foul, why destructive to health, Soup, why keeps hot longer than water, 



Shade, why cool in the summer, 150 'Sparks of fire, what arc, 7 



why objects seeui dark in, 252 Specific gravity defined, 62 

 Shadow, what is a, 244 iSpeetacles best suited for old people, 265 



Shaft of a column, 46 Spoon, metal, how retards the boiling of a 



Sheets of a bed why feel cold, and the kettle, 150 



blankets wann, 152 why tarnisbod by the yolk of eggs, 



Ship at sea, why the masts are seen before 304 



the hull, 253 Spray of waves, cause of, 61 



Ships, iron, why do not sink, 65 Springs, effect of drainage upon, 53 



Sbces, hotter for being dusty, 172 Stones for building, bo\v" to estimate their 



Skull, the form of the, embodies the prin- durability, 43 



ciples of the arch, 44 building, action of the weather 



Sight, difficult after leaving a lighted room on, 48 



and going into the dark^"266 why lifted easier in water than on 



Size, 4 land, 65 



Skating swiftly over thin ice, effect of, 27 Stove, advantages over an open fireplace, 

 Skin, cleanliness essential to the healthy 



action of, 237 

 Sky, why appears blue, 271 

 Sleet, what is, 92 

 Smoke, what is, 218 



why ascends, 13 



Smoking, how preserves meat, 808 

 Sneezing, what is, 123 



Snow, at the foot of a wall, why melts Stucco, what is, 



disadvantages of, 219 



why crackles in cooling, 186 



why crackles when a fire is kindled 



in it, 1S6 



Stones, why not suitable for fuel, 226 

 Straw, use of, in the Egyptian bricks, 40 

 Stripes, effect of, in dresses, 279 



rapidly, 161 

 flake, how formed, 93 

 heat of, how shown, 138 



Sucker, the common, 72 



Suction, height to which water may bo 



raised by, 98 

 how diminishes the darkness of 'Suffocation, how occurs, 123 



night, 270 |Sugar and salt, how flavor water, 67 



how protects the surface of the earth salt, &c., retard boiling, 157 



in winter, 92, 93 

 melting absorbs heat, 138 

 various colors of, 94 

 what is, 92 

 why none in summer, 93 



white, 93 



Soap-bubble, origin of colors in, 259 

 Soap, utility of in washing, 57 

 SoiC a bad conductor of heat, 136 

 effects of on temperature, 107 

 Solid, what is a, S 

 Solution, what is a, 193 



when saturated, 193 

 Sonorous bodies, what are, 116 

 Soot, smell of, why sometimes noticed in 

 a room, 216 



of, 71 



best conductors of, 120 

 how obstructed by fogs, rain, &c., 



119 



how produced, 114 

 louder by night than by day, 119 

 not heard alike by all persons, 120 

 velocity of, 118 

 bounds, musical, what are, 120 



origin and transmission of, 114 

 rejection of, 124 

 transmission of by solids, 117 

 vibrations, to what compared, 117 

 vibrations in solids, how rendered 



visible, 118 



Sulphur, product of when burned, 393 



Sulphureous acid, 303 



Sulphuric acid, 304 



Summer, Indian, haziness of, 87 



Sun, seen through a fog appears red, 87 

 the, a source of lu-at, 132 

 weight on the surface of, 19 

 why appears large on the horizon, 269 



Sun's heat, why greater in some portions 

 of the earth than in others, 133 



Sunbeam, motes floating in, what arc, ICO 



Sunset, red, cause of, 86 



Surf, what is, 61 



Surfaces, some, why brilliant, 242 

 dull, 242 



Swimmers, unskilful, why sink, 63 



VJound, air necessary for the production Swimming why easier in salt than in fresh 



water. 63 

 philosophy of, 63 

 Springs in ponds prevent freezing, 163 

 mineral, cause of, 54 

 origin of, 51 



why cool in summer, 150 

 why often fail in dry weather, 51 

 Sprinkling a hot room how cools it, 198 

 Squinting, occasion of, 268 



occasions double vision, 267 

 Starch, how manufactured, 302 



may be converted into sugar, 303 

 what is, 302 



why necessary to boil before using, 

 802 



34* 



