2I4f 



EXPERIMENTS ON LIGHT. 



convulfive raovements", that took place, noiwithHanding every 

 time the wires were made to touch each other completely. 

 Thus we have a freQi proof of the identity of the fluid fet 

 in motion. by the pile of Volta, and by a common eledrical 

 machine. 



XVII. 



Experiments on Light; hy Mr. KirTt-K, ef Jena. Communicated 

 bjj Dr. ORSTEu.f 



Hsifchcl's dif- ^ HE imporiant difcovery of invifible folar rays, with which 

 cuvery of invi- Herfchel has enriched natural phifofophy, has given occafion 

 has given rife to ^" another little known, even in the country where it has been 

 another.. made. 



Our knowledge Our knowledge of light had made no perceptible advance- 



^''''gt^^^^^*^'^"^ment fince Newton, when Herfchel found, that all the phe- 

 fince Newton 5 , . ri-ii 



nomena occurrmg durmg tffe decompolUion or hght by means 



of the prifm had not yet been noticed. Philofophers had con- 

 tented themfelves with perceiving different colours, without 

 examining by other procefTes, whether phenomena impercep- 

 till Herfchel tible to the eyes did not take place. Herfchel, by means of 

 found, that in- j^[^g thermometer, difcovered invifible rays exterior to the folar 

 jond the fp'cc- Tpeflrum, that potTefs the property of raifing the mercury, 

 trum, raifed the Mr. Rifter repealed his experiments with fuccefs; but con- 

 Ritter, repeating ^^*^'''"d> that the different rays of light produce very different 

 the experiment, chemical changes in bodies fufceptible of them, heconceived, 

 J^h;ht conu'ned'*' '•^^^'^'Sht likewife contained invifible rays, which a6led che- 

 iiivifible rays mically. He expofed muriate of filver to the aftion oflhe 



aGing chemical. (-^,^^ fpearum, and found his conjeaure fubftantiated: the 

 ly likewifc; and _ ' ■' 



found, that muriate of filver very foon became black beyond the violet 

 muriate uffilver,g(^j^e of the fpeflrum; blackened a little lefs in the violet it- 

 fpeftrum, grew fclf; and ihis action was fiill lefs in the blue, diminifliing thus 

 blackeft beyond ,y,ore and more in proportion to the difiance from the violet, 

 and^the^effclt^di-till it became null. On expofing muriate of filver a little 

 minifhed in pro- blackened, that Is to fay, a little difoxigenated, to the fame 

 Jiftanceftom^ adion of light, its whitecolour was partly reflored by the red 

 this, _ ray, and ftill more by the invifible ray beyond it. 



and the muriate 



naild'had^hs'^" * "journal cie Phjfique, December, 1803, Vol. LVII. p. 409. 

 colour partly re- The 



^orcd by the in- 



