44 Inquiries into Coloured Ligbt. 



various colours, as that of fuipbiir, blue; that of copper 

 opened with lublimate, ereen," &c. 



To invefiigatc this analojxv accordincf as the various lights 

 which come to our fcnfes prefciit thcnifcives to us, 1 iiere 

 tiircclcd my inquiry, ift, To Itarn what coiours tiie various 

 iniianicd vapours of terredrial bodies combured in our atnio- 

 fphere throw out : adiy, Whether thcfc colours were homo- 

 geneous; and if not, 3illv, How far thev oblerved fueh fimi- 

 lar rcfra(i:tions in their Jecompofnion as the folar light doth. 

 From the ground of a fpeculative opinion, which I have long 

 entertained in my own mind, that, although the white hicicl 

 light of the fun is only a compound, vet light as lio;ht exilts ia 

 a lucid, homogeneous, elementary, wh.iicand uncompound- 

 ed (Kite, and only becomes otherwife by mixing or palfini» 

 throuoh oxygenous and other airs, or fuch vapours as refult 

 from combultion, and, by being fuffiifcd with th.e ccdours fur- 

 niflicd by thefe, becomes lefs and lefs pure, and, conrequently, 

 tainted with colours. I applied niv obfervations Hrft to the 

 electric fpark. From the inftantaneous and tranfient natuixi 

 of this light, the dccompofition could not be examined : it is 

 known, however, that ele6lric light palled through anexhaufted 

 receiver exhibits tremulous ravs of various colours fomewhat 

 fimilar to the aurora horcalis; fo that it conies but that this 

 li<;ht is a compound. The next light which met mv attention 

 was that of the fparks of iron deflagrated in vital air. Although 

 I could not examine this by experiment for the fame realbrx 

 as before, yet I may venture to pronounce that, this being" 

 nothing but the white heat of fufed iron, it muft be a ccjrii- 

 pound light. The nextWas the very brilliant light of phof- 

 phorus burnt in vital air, fo blazingly bright, that no eye , 

 can (land the firft llrokc of it. The next was the. lucid 

 lia'ht of camphor inflamed bv fpirlt of wine, whole blue 

 may be fuppofcd, in i()me degree, to tinge the brilliancy of 

 xhe white: thcfe decompofed into a faint fpec^rum ot 1.h,e 

 principal colours. The next was the light of fj)ermacelj 

 bnnit in Argand's lamp, wherein the fmoke i|; m great 

 meafurc confumed. This was faid bv Dr. Franklin to conic • 

 the ncarotl to day-light of anv other terrcltrial light. This 

 dccompofes into red and yellow, fomewhat greenilli as it 

 runs into the blue. The flame of wax was llie next light : 

 this has a fulTufion c^f yellow, and decompolcs into a red and 

 greenifli yd low and blue. The flame of tallow was the next, 

 which Sir Uaac Nevvlon calls yellow: this decompolcd into 

 a red, a blueifli green, and blue. 



From the ground of a reafoa which will be given bolow, 



Ibciiau 



