INDEX. 



623 



DOC 



Doctrine of descent of animals, 

 origin of, 603-604: 



Dollond's invention of achromatic 

 lenses, 477 



Donders's ' Noematachograph,' 56 



Double refraction of light, dis- 

 covery of, 224 



stars, discovery of five hun- 

 dred, 582 



Doubtful ideas, duty of avoiding, 

 111 



Dove's discoveries respecting in- 

 duced electric currents, 493 



Drebbel, improvement of ther- 

 mometer by, 479 



* Dry column,' DyckhofFs, 481 



Duality, the law of, 343 



Du Bois Keymond's discoveries, 

 574 



Du Fay's discovery of the * elec- 

 tric kiss,' 567 



of two kinds of electri- 

 city, 533, 577, 591-592 



Dyckhoff's ' dry column,' 481 



Dynamic causes, 407, 417 



phenomena, essential elements 

 of, 447 



EAKTH, attraction of bodies by 

 the, 526-527, 558 



currents in telegraph wires, dis- 

 covery of, 569 



discovery of the specific gravity 

 of the, 586-587 



of the true shape of the, 



608 



Eck de Sulsbach, the first to ob- 

 tain oxygen, 501 



Education of the power of com- 

 parison, 330-331 



of imagination, 369- 



371 



of inference, 40 



of the will, 131 



Effects, how determined, 430 



multiplication of, 415 



proportionality of to causes, 416 

 Elasticity of air, discovery re- 

 specting, 526 



ELE 



Electric action through glass, dis- 

 covery of, 532 



attraction, discoveries respect- 

 ing, 531 



balance, invention of, 486 



charge of telegraph cables, dis- 

 covery of, 235, 496 



of underground telegraph 



wires, discovery of, 568-569 



condensers, invention of, 481 



conduction, discovery of, 553 

 resistance of metals, dis- 

 coveries in, 486 



of liquefied carbonic acid, 

 543-544 

 of rarefied gases, 555 



currents, discovery of induced, 

 493 



in animal tissues, discovery 



of, 574 



distribution, laws of, 481 



exploring wires,' employment 

 of, 481 



induction, discovery respecting 

 static, 567 



instruments, discovery by 

 means of new, 479 



* kiss,' discovery of, 567 



kite experiments, 534 

 invention of, 480 



machine, discovery of advan- 

 tage of warming an, 531 



improvement of the, 480 



invention of, 480 



pencil of rays from a point, 

 discovery of, 567 



repulsion, discoveries respect- 

 ing, 533, 567 



sparks, discoveries respecting, 

 533, 567 



spectra in rarefied gases, dis- 

 coveries respecting, 536 



telegraph, invention of, 537 

 Electricity and lightning, dis- 

 covery of the identity of, 534, 

 592 



and magnetism, hypothesis of 

 the decomposability of, 520- 

 521 



animal, discovery of, 491-492 



