on the terrestrial Rays that occasion Heat. 535 



Dark-violet paper 



scatters 



75 ra y s °f 



light, 



Brown paper 



- 



101 



- 



- 



Black paper, with 



a strong gloss 



420 



- 



- 



Black satin 



- 



102 



- 



- 



Black muslin, sus 



pended 



64 



- 



- 



Black muslin, upon black muslin 



18 



<" 



- 



Black worsted 



- 



16 



- 



M» 



Black velvet 



- 



7 



- 



- 



Tin-foil 



- 



- 8483 



- 



- 



Iron 



- 



10014 



- 



- 



Copper 



- 



13128 



- 



- 



Brass 



. 



- 43 8 58 



- 



- 



Gold-leaf paper 



- 



124371 



- 



IB 



I cannot help remarking, that in making these last experi- 

 ments, I found that black paper could not be distinguished from 

 white ; and that, pn bringing it a little nearer to the light than 

 it should be to make them perfectly equal, any of my friends 

 who happened to be present, would mistake the black for the 

 white. 



EXPLANATION OF THE PLATES. 



Plate XX, represents the spectrum of heat A, S, Q, A ; and 

 of light G, R, Q, G. If a prism be placed in a window, so as 

 to throw the colours of light upon a table, and Plate XX be 

 laid under the colours, so that they may respectively fall upon 

 the places where their names are inserted, then may these co- 

 lours be made to fit into their proper spaces, by lowering or 

 raising the prism, at pleasure. When the colours occupy their 

 proper situations, the line A Q will express the space over 



3Z2 



