INDEX, 



445 



Column, height of, kow measured, 121 



what is a, 121 

 Compass, mariner's, 4-4 



ordinary, 4-'4 



when discovered, 426 

 Compressibility, what is, 16 

 Concord in music, 196 

 Condensation, what is, 238 

 Conduction of heat, 216 

 Convection of lieat, "16 

 Cordage, streTigth of, on what depends, 113 

 Corit, why floats upon water, 43 

 Cornea, what is the, ^49 

 Coulomb's torsion balance, 382 

 Countries destitute of rain, 279 

 Coughing, sound of, how produced, 204 

 Cranes, what are, 105 

 Cranio defined, 110 

 Cream, why rises upon milk, 147 

 Crying, what is, '205 

 Cuppinji, operation and principle of, 175 

 Currents, electric, how exert their influence, 



4-23 

 Cylinders, strength of, 118 



Dagnerreotjrpes, how formed, 345 



Dead point explained, 112 



Declination of needle, 426 



Density, what is, 15 



Derrick, what is a, 105 



Dew, circumstances that influence the pro- 

 duction of, '271 

 does not fall, 271 



phenomena and production of, 270 

 when deposited most freely, 271 



Dew-drop, why globular, 30 



Dew-point, 270 



not constant, 270 



Diamagnetic phenomena, 441 



Diamagnetism, 441 



Dioptics, 313 



Directinn, line of, 40 



Discord in music, 196 



Distillation, '242 



Divibibility, 13 



Dovetailing, what is, 117, 118 



Drainage, principles of, 152 



Draught of chimney, 262 



Dresses, black, optical effect of, 333 



Drops, prescription of medicine by, unsafe, 

 29 



Ductility, what is, 26 



Dust, how we free our clothes of by agita- 

 tion, 20 



Dynamometer described, 89 



E 



Ear, construction of, 201 , 202 

 Earth, bodies upon, why not rush together, 

 30 

 cause of present form of, 83 

 centripetal force at equator of, 83 

 how proved to be in motion, 84 

 the physical features of, how affect 



winds, 282 

 the reservoir of electricity, 376 



Earth, telegraphic communication through, 



4o7 

 Earth's attraction, law of, 32 

 Ebullition, what is, 241 

 Echo, conditions for the production of, 198 



what is, 197 

 Echoes, when multiplied, 198 



where most frequent, 198 

 Egg-shell, application of the principle of the 



arch in, 1'20 

 Elastic bodies, results of collision of, 68 

 Elasticity defined, 22 

 Eel, electrical, 391 

 Electric attraction, 370 



currents, how eiert their influence, 



429 

 fluid non-luminous, 88T 

 light, 410 

 repulsion, 370 

 shock, 383 



spark, duration of, 888 

 Electrical battery, 3S4_ 

 induction, 377 

 machines, 378 

 Electricity a source of heat, 212 

 atmospheric, S91 

 conductors and non-condnctort 



of, 273 

 Du Fay's theory of, 271 

 Franklin's theory of, 271 

 effect of on a conductor, 386 

 experiments of Franklin with, 



392 

 frictional, distinctive character 



of, 407 

 galvanic, how excited, 401 



how differs from ordi- 

 nary, 300 

 how discovered, 388 

 quantity of, what is, 



408 

 theory of, 402 

 intensity of, what is, 



408 

 what is, 398 

 how evolves heat, 409 

 how excited, 369 

 how exerts a magnetic force, 431 

 influence on the form of bodies 



376 

 kinds of, 370 

 magneto, 437, 438 

 cf vital action, 391 

 positive and negative, 272 

 quantity necessary for decompo- 

 sition, 412 

 real character of unknown, 403 

 secondary currents, 437 

 thermo, what is, 416 

 velocitv of, how determined, 389 

 what is, 369 



where resides in bodies, 876 

 Electro-magnetism, 429 



magnets, how formed, 432 

 what are, 432 

 Electrometer, 381 

 Electro-mctallur^y, 413 

 Electrophorns, 380 

 Electroscope, 381 

 Electrotyping, 413 

 Electrodes, what are, 413 



