194 GENERAL CONDITIONS OF SCIENTIFIC RESEARCH. 



CHAPTER XX. 



EELATIVE FREQUENCY OF DIFFERENT KINDS OF DISCOVERIES. 



As no discovery can be made until its conditions are ripe, 

 and as an accumulation of lesser truths is usually requisite 

 to ripen the conditions of discovery of a greater one, great 

 discoveries cannot often be made. The relative frequency- 

 of different kinds of discoveries varies generally as their 

 degrees of intrinsic importance. In every science, small 

 facts and comparatively unimportant phenomena are 

 abundant, whilst general laws and principles are but few. 

 The discovery of a new force is even much more rare than 

 that of a general principle ; no really new force has been 

 discovered since those of electricity and magnetism in 

 ages past ; the nearest approach to such a discovery was 

 that of chemical-electricity, by Volta, at the end of the 

 eighteenth century. As the great general relations of 

 forces to each other must of necessity be more nume- 

 rous than the forces themselves, so we accordingly find the 

 discoveries of such relations more frequent. Several, 

 viz., chemico-electric and electro-chemical action, thermo- 

 electricity, electro-magnetism, magneto-electricity, &c., 

 have all been found within the last one hundred years. 

 Discoveries of simple bodies also must of necessity be 

 much less frequent than those of their compounds, because 

 each simple substance is capable of forming a great many 

 combinations with other simple substances, as well as 

 additional permutations in isomeric compounds. Since 

 the year 1800, only about thirty elementary substances 

 have been found, but during that time many hundreds 

 (if not thousands) of compound bodies have been dis- 

 covered. Discoveries of simple existences, whether of 



