and the Determination of White Light. 



221 



The source used in this experiment was the Argand burner 

 like the one used back of a Methven screen. The coefficients 

 represent tenths of a millimetre required to make the match, 

 and the fractions before W represent the ratio of the two 

 slits. For the amyl-aeetate lamp the following equations were 

 obtained: — 



Table III. May 13th, 1896. 



1. 30(30-5) 4-11 1(69-5) = 16/150 W. 



60(11) + 26(54-5)= 13/150 W. 



40(15-5)4- 60(57) =14/150 W. 

 45(18-7)+ 83(37) =15/150 W. 

 28(23-5)+ 90(59) =24/150 W. 

 30(29-5)+ 92(64-5) =24/ 150 W. 



A second determination of the wave-length corresponding 

 to positions on the scale was made necessary by a readjustment 

 of the instrument. In this determination 25 bands were 

 visible. 



Table IV. May 14th, 1896. 



Scale. 



Wave-length. 



Scale. 



Wave-length. 



10 



803x10-7 cm. 



738 



687 



643 



603 



569 



538 



486 



46 



469x10-7 cm. 



452-7 



435 



420-4 



405 



389 



376 



365 



355-6 



14 



50 



18 



55 



22 



60 



26 



65 



34 



70 



38 



42 



75 



80 





For the Carcel lamp the following set of equations were 

 obtained : — 



Table V. 



1. 33(191)+140(54)=W. 



2. 20(25) + 56(59)=W. 



3. 25(14-2)+ 73(56)=W. 



4. 27(20) + 78(57-5) =W. 



5. 17(22-5)+ 10(35-3) +18(50)=W. 



6. 22(23) + 16(35-25)+17(46)=W. 



Maxwell gives as the mean of twenty observations the 

 following equation for white light in terms of his scale: — 



18-6(24) + 31-4(44)+30-5(68)=W. 



Transforming to terms of the above scale it becomes: — 



18-6(23-5) +31-4(35) + 30-5(45-5)= W(?) 

 Phil. Mag. 8. 5. Vol. 46. No : 279. Aug. 1898. R 



