Permanent Colours of Op ah Bodies, 227 



bined, confequently the fpaces, which intervene 

 between thofe particles, are equal to each other: 

 and the fpace alfo which intervenes between the 

 furface of the giafs, and the arfenical particles 

 which are neareft to the furface, is equal to the 

 intervals which intercede the particles. And this 

 may be farther fhewn, by breaking foch maffes 

 of glafs ; for, the frcfh furfaces of every frag- 

 ment will appear fimilar to the original furface 

 of the whole mafs. 



From hence it is evident that, when a fmaller 

 portion of arfenic is mixed with glafs, the inter- 

 vals between the White Opake Particles will be 

 larger, and therefore, the lefs refrangible rays will 

 be more copioufly tranfmitted through them: 

 and, in confequence of their lofs, the more re- 

 frangible rays which are intercepted, and re- 

 fleded, by the particles of arfenic, will exhibit 

 a bluer colour, and recede farther from white- 

 nefs. 



This obfervation is confirmed by experiment : 

 for, although glafs, which contains a fmall pro- 

 portion of arfenic, appears blue by incident, and 

 orange coloured, by tranfmitted light; if a laro-e 

 proportion of arfenic be combined with the o\^Sy 

 the compound, viewed by incident light, ap- 

 pears white, and no colour is tranfmitted through 

 it, except it be made extremely thin. For, as 

 the intervals between the particles, which are 

 thus denfely difpofcd throughout the ghfs, da 



0.2 not 



