Manner in which Xatural Bodies exhibit Colours. 201 



The experiments arrange themselves under the folloxA ing 

 heads : 



1st, On the affinities which exist betwixt hme, clay, and 

 silex, and carbon, in temperatures from 130° to 170*^ of 

 Wedgewood. 



2d, On the affinities which exist betwixt carbon and ores 

 variously compounded, judging comparatively from their 

 metallic lesults in fusion. 



3d, On the affinities which exist betwixt carbon and pri- 

 marv and secondary ores of iron, arranged according to tlieir 

 former classification, judging also comparatively from their 

 metallic results. 



[To be continued.] 



XXXV. Researches in regard to the 3Janner in iihich Nia- 

 tural Bodies exhibit Colours, and Experiments on a neiu 

 Theory of that Phceiiometiou. Bij S. F. Hermbstadt*. 



First Part — uhich contains an Examination of the Ques- 

 tion, IVkether Light be a simple Sabsla/iceP 



J. HE colour of any object considered as a phosnomenon is 

 the result of the sensation impressed on the organ of «ight 

 by the effect of the object, and can no further be explained. 

 If the result of this eflect is to be defined from physical 

 causes, it is then necessary to follow its producing causes 

 to discover them if possible, and to deduce from them a 

 rational explanation consistent with natural principles. 



If we set out from any other principle, the effective causes 

 are considered as accessory things ; and no other result can 

 be obtained from our researches than hypothesis susceptible 

 of any modification, and for that reason insufficient. 



It was from this principle that the antient philosophers 

 proceeded when they wished to give a proper idea of the 

 production of colours ; and therefore it was natural that the 

 hypothesis they formed should be subject to any modifica- 

 tion, and readily give place to other hypotheses. 



Newton himself, who without doubt is the greatest among 

 the modern philosophers, did not render his hypothesis in 

 regard to light and colours peri'cctly free from this objec- 

 tion. The experiments which he first made in the year 

 1G6G on the refraction of iight, gave him reason to observe 



* Ffom Nciies Allgrn;cinr5 Journ.J da Cbcmtc, by Ilcrmbotjclt, Klip- 

 rotli, &.C. vu!. ii, no. i. btfiin liioj. 



its 



