178 GENERAL CONDITIONS OF SCIENTIFIC RESEARCH. 



The origin of many important discoveries lies buried 

 in the obscurity of past ages : for instance, those of weight, 

 light, heat, electricity, magnetism, chemical action, gold, 

 silver, mercury, copper, iron, lead, tin, bronze, amalgam 

 of gold, sulphur, carbon, coal, asphalte, rock-oil, vermilion, 

 corrosive sublimate, chloride of silver, lunar caustic, real- 

 gar, white arsenic, diamond, precious stones, salt, nitre, 

 soda, borax, glass, earthenware, ochre, wood, various dyes, 

 ink, paper, wine, vinegar, numerous astronomical dis- 

 coveries, and many others. Many discoveries are forced 

 upon us. Human beings, even in the very earliest times, 

 must have discovered the existence of mechanical force, 

 the sun, moon, and stars, the occurrence of day and 

 night, eclipses, the seasons, tides, rain, wind, lightning, 

 thunder, earthquakes, and a multitude of other familiar 

 phenomena. 



Great discoveries usually shed halos before them, 

 which for a time appear mysterious. The questions of the 

 globular form of the Earth, and of the possibility of 

 reaching India by sailing to the West, were great mysteries, 

 and led to the discovery of America. In quite recent 

 times the remarkable lines of Fraunhofer were, during 

 many years, also a great enigma, and attracted many 

 eminent investigators to try to discover their meaning. 

 Wollaston, in 1802, was the first to observe the dark 

 bands in the solar spectrum. Fraunhofer, in 1815, 

 measured the positions of many of them, and made a map 

 of more than six hundred. He also examined the light of 

 the fixed stars, the electric spark, a candle, &c., and found 

 two things, viz., that the same kind of light always gave 

 the same set of bands, and that different kinds of light- 

 gave different sets of bands. After him, at various 

 intervals, numerous investigators examined various parts 

 of the subject ; amongst these were Herschel, Brewster, 



