2$6 MAGNETIC PROPERTY OF NICKEL. 



raJJel to each other, on account of the different refrangibility 

 of the light of which they confift. Thus the broken line of 

 the extreme red, which confifh of the longeft portions, is leaft 

 refra&ed : the other reds follow, and are placed in contact 

 with the firft, and with each other, but on account of the 

 different magnitude of the portions, fomevvhat obliquely. The 

 dark fpaces alfo are in contact, and form a feparation between 

 each portion of light. In the fame manner, the green follows 

 the red, with little or no vifible yellow. The blue and violet 

 are fomevvhat mixed : for thefe two colours are much lefs 

 widely feparated by thin plates than by the prifm : for this rea- 

 fon, each portion of light formed by the contiguous lines of 

 the different colours is bounded not by flraight but by curved 

 lines. 



It is evident that, by drawing a line acrofs this compound 

 fpectrum at any part, we may learn the component parts of 

 the light conftituting the rings at that part; for the prifm only 

 fpreads the colours in a direction tranfverfe to this fpeftrum : 

 and it may be obferved, that after the eighth or tenth alterna- 

 tion, the light tranfmitted at each point is fo mixed, that we 

 may eafily underirand how it appears white. 

 Colours by The colours of thin plates, as feen by tranfmiffion, are alfo 



aoTfoldlTntr ea % exhibited in the folar microfcope ; but, fince it is ut- 

 geouflyfhewn. terly impoffible to exclude the very great proportion of the 

 light whicli is not concerned in their formation, they never 

 appear fo brilliant as the colours feen by reflection. 



Y. 



XL 



Extract of a Letter from R. Chlnevix, Efq. on the Magnetic 

 Property of Nickel. 



Nickel is mag- 1 AM afraid that I was too hafty in denying the magnetic 

 property of nickel. The fa£t is, I had obtained both it and 

 cobalt in that Hate. But in profecuting a feries of experi- 

 ments upon thefe metals, I perceived the real caufe why fe- 

 veral fragments which I had obtained did not exert any in- 

 fluence upon the magnet. I took a piece of nickel which was 

 not attractable, and which exhaled arfenieal vapours when 

 4 heated 



netic 



