temporarily produced in Isotropic Bodies. 



M5 



charge P in kilogrammes. This latter acts as a pressure, and 

 the weight of the chest E, of the hook e and the press A, are 

 comprised in the charges stated in the table. 



Colour of the 

 image E. 



Crown 

 glass. 



Elate 

 glass. 



Crown glass 

 of Clichy, 



P. 



Flint 

 glass. 



Alum. 



Very black 



Black 



Bluish 



Blue 



White 



Yellow 



Orange ... 



Red 



Violet 



Indigo 



Blue 



Green 



Yellow 



Orange 



Bright red 

 Deep red . . . 



Purple 



Indigo 



Blue 



Green 



Yellow 



Orange 



Bluish-red 



1 

 2 



2| 



5i 



7i 



8 



9 



14 



15i 



162 



19| 

 21 



23f 

 25^ 



27f 



29 



32 



15 

 32 

 40 

 72 

 100 

 130 

 140 

 155 

 170 

 190 

 212 

 240 

 260 

 287 

 290 

 300 

 310 

 325 

 370 

 395 

 430 

 465 



150 

 16-0 

 16-6 

 13-7 

 141 

 16-3 

 15-5 

 13-9 

 13-2 

 13-6 

 140 

 14-7 

 151 

 15-7 

 14-7 

 14-3 

 140 

 13-9 

 14-7 

 14-6 

 14-8 

 14-5 



40 

 90 

 100 

 210 

 300 

 370 

 420 

 480 

 520 

 560 



400 



45-0 



41-7 



400 



42-2 



46 



46-7 



42-9 



40-5 



400 



10 

 25 

 32 

 66 

 90 

 110 

 138 

 144 

 150 

 184 

 205 

 242 

 251 

 280 

 295 

 310 

 320 

 334 

 370 

 391 

 423 

 466 



100 

 12-5 

 13-3 

 12-6 

 12-7 

 13-8 

 15-3 

 12-9 

 11-7 

 13-1 

 13-6 

 14-9 

 14-6 

 15-3 

 150 

 14-8 

 14-5 

 14-3 

 14-7 

 14-4 

 14-6 

 14-6 



30 

 58 

 80 

 145 

 175 

 230 

 257 

 295 

 320 

 360 

 420 

 475 

 515 

 550 



300 

 290 

 33-3 

 27-6 

 24-6 

 28-8 

 28-6 

 26-4 

 250 

 25-7 

 27-8 

 291 

 29-9 

 3001 



30 

 60 

 80 

 150 

 225 

 248 

 300 

 352 

 410 

 450 

 492 



300 

 300 

 33-3 

 28-6 

 31-6 

 31-0 

 33-3 

 31-5 

 320 

 321 

 32-5 



It is evident that the differences of the paths of the two rays 

 are sensibly proportional to the charges, still the variations which 



P 



subsist for the same piece in the values of the ratio — suffi- 

 ciently indicate that the procedure is not capable of furnishing 

 very exact results. 



In point of fact, each of the colours exhibits a gr§at number 

 of degradations, and however careful we may be to choose the 

 most decided tint, and that which accords best with the desig- 

 nation of Newton, it is hardly reasonable to hope that we shall 



