INDEX. 



629 



HYD 



Hydrochloric acid, discovery of its 



non-chemical action upon lime, 



239, 550 

 Hydro-electricity, discovery of, 



235, 493-494, 568 

 Hydrofluoric acid, investigation 



of anhydrous, 502 

 Hydrogen acids, discovery of, 557, 



600 



discovery of, 540 



the liquefaction of, 560 



Hyponitrous acid, discovery of, 



552-553 



Hypotheses and questions, dis- 

 covery by devising and testing, 

 508-524 



as aids to discovery, 134, 363- 

 367 



how formed, 365, 369-370, 401 

 how to treat unproved 



ones, 123 



scientific, 362 



untrue ones as an aid to dis- 

 covery, 514-515 



use of inference in devising, 

 358-359 



value of scientific, 367 



yet remaining to be proved, 

 513-514, 605 



ICE, discovery of heat evolved 

 by friction of , 530 

 of the stationary tempera- 

 ture of melting, 566 

 Iceland-spar, electric excitement 



of, 535 



Idea of an Infinite Cause, nature 

 of the, 49-50, 403-404, 409-410 



of creation, nature of the, 158 

 Ideas, abstruse, 48 



acquisition of, 43, 47 



association of, 67 



axiomatic, 48 



conformability of to their 

 causes, 42 



classification of, 44, 53 



duty of avoiding doubtful, 111 



false ones often unavoidable, 

 102, 112 



IMA 



Ideas, fixation of, 59 



flow of, 54-55 



formation of general. 400-401 

 of new, 336-342, 365, 370 



how many can we perceive at 

 once ? 46 



mediate, 353 



and immediate, 51 



necessity of correct, 45 



purification of, 147 



persistency of, 65 



qualitative and quantitative, 51 



quantification of, 51-52, 341, 

 359, 451 



recognition of, 63, 67 



recollection of, 67-71 



relative degrees of complexity 

 of different, 45-46 



of distinctness of dif- 

 ferent, 47 



seat of, 36 



selection of, 62, 97, 98 



sources of scientific, 42, 51 



suggestion of, 68 



time required for perceiving, 

 47,60 



transformation and analysis of, 

 illustrated, 337-340 



true ones, how detected, 156- 

 157 



the basis of intellect, 45 



ultimate scientific, 49, 409 

 Identity of electricity with light- 

 ning, discovery of the, 534, 592 



from various sources, 509 



the law of, 343 



Ignorance, effects of in research, 

 25, 112, 133, 210-211 



probable extent of, 23, 26 

 Ignorant hostility to scientific 



genius, 267 



Imagination, definition of the 

 power of, 360 



the mental process of, 367-368 

 power of, how cultivated, 



369-371 



Imaginative power, conditions of, 

 361 



necessity of, to great suc- 

 cess in research, 241 



