45 Inquiries into Coloured Light. 



As fubftances acidified bv oxygen " drff'er from each other 

 only according to the feveral natures of the oxygenated or 

 acidified bafes," why may not this be the cafe of coloured 

 flame or vapour? Their colour differs only according to the 

 nature of the bafes thus illuminated by their combination 

 with light. 



In examining and obfervlng upon thefe fa6ls *, both by 

 prlfms and lenses, in this comparative view, it appeared thefe 

 lerreftrial coloured llames and aciriform vapours conibured in 

 our atmofpheric air, obferve the iame laws of refraftion and 

 decompolitlon as the folar liijlit in every inftance which can 

 be brought under experiment. And that, as the folar light 

 proceeds from inflamed vapour on the furface of the fun's 

 atmofphere, as Dr. Hcrfchel flates, this folar light muft arife 

 from vapours having fimilar bafes as thefe terreltrial coloured 

 lights have, allowing for an apparent diflerent purity; and muft, 

 having the fame properties, be of the fame nature. So that, 

 althoutih the folar light, coming to our fight in its compound 

 Itate, is a bright lucid light; yet, being decompofed by the 

 different refradlons, which the fevcral fubftances or bafes 

 from which it proceeds are liable to, it is refolved, exactly as 

 the terreltrial lights above examined are, into the conftituent 

 coloured lights which the feveral baft'S give out. 



I will not venture, on the ground of the obfervations ftatcd, 

 and on the reafoning attached to them as above, to lay it 

 down as a propofition abfolutelv proved; but will hazard f 

 it as a quaere, open to further inVeiligation. 



Mav not the fun, an unignited body, and fimilar to our 

 terreftrial globe in all its external appearances, (but poffibly 

 of variety in its mineralogy,) prodqee an atmofphere of more 



* Tt is hardly wortli while to dcl'cribe the tiiLthod I obfcrvcd to do this, 

 vet it may not be" amils. 1 had prepared a tall lonj; box, painted black on 

 the iiilkle, v.ith a fliding door in the from, in which was bored a hole 

 about half an inch dianiettr : the ufe of tlvis llidiiig door was to raife or 

 lower the hole to the height of the coloured light which I had.occafion to 

 try. There was alio a door on the Tide by which to put in the lights, and 

 a valve at the top to let out the fmoke when 1 ftiould obferve that it af- 

 fefted the lij^ht. By applying a prifm to this hole, 1 obtained from all the 

 lights, cxcejir the blue, a prifmatic Ipcdtrum : the light of the blue was io 

 weak, that J coul.l not obtain a ipctirum from it coming tliiough the hole ; 

 I therefore drew up the fliding-door entirely, and fo turning the prilm Ai 

 to diredt the refracted rays down upon the ground near under the table on 

 v.hich the box flood, and into tlie dark, obtaincil, yet imperfectly, the fpec- 

 truin above noticed. By lenses applied to the hole, the dillertnces of the 

 difterent focHscs were as the refraftions inverlely. 



t This J ftatcd to Dr. Htrfchcl by letter, dated March 17, 1797 ; and 

 had afreiward a conveif.iiion with him at Slouijh on this fiibjedt of the 

 coiouied rays of llie tbiar lis^ht. 



fublimed 



