4 PEOFESSOE TYNDALL ON CALOEESCENCE. 



in the first column of figures in the Table. It was found convenient to call the maxi- 

 mum efiect in each series of experiments 100 ; the second column of figures, obtained 

 by multiplying the first by the constant factor 1"37, expresses the heat of all the parts 

 of the spectrum with reference to this maximum. 



Table I. — Distribution of Heat in Spectrum of Electric Light. 



Movement of pile. Value of deflection. Calorific intensity, in lOOths 



of the maximum. 



Before starting (pile in the blue) . . 0*0 0*0 



Two turns forward (green entered) . 1-6 2*0 



3-6 4-8 



5-6 7-5 



„ (red entered) . . 15'5 21-0 



„ (extreme red) . . 32-6 44-6 



Half turn forward . . . . ... 44-0 60-0 



540 74 



62-0 85 



70-0 95-8 



72-5 99 



Quarter turn forward, maximum . . 73*0 100-0 



' „ 70-8 97-0 



Half turn forward 57-0 78-0 



45-5 62-0 



....... 32-6 44-5 



26-0 35-6 



Two turns forward 10-5 14-4 



6-5 9 



5-0 6-8 



„ 3-5 5 



2-5 3-4 



1-7 2-3 



1-3 1-8 



Here, as before stated, we begin in the blue, and pass first through the visible 

 spectrum. Quitting this at the place marked " (extreme red)," we enter the invisible 

 calorific spectrum and reach the position of maximum heat, from which, onwards, the 

 thermal power falls till it practically disappears. 



In other observations the pile was first brought up to the position of maximum heat, 

 and moved thence to the extremity of the spectrum in one direction. It was then 

 brought back to the maximum, and moved to the extremity in the other direction. 

 There was generally a small difference between the two maxima, arising, no doubt, 

 from some slight alteration of the electric light during the period which intervened 



