390 Prof. Tyndall on Calorescence. 



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 ther- 

 mal 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 direc- 

 tion. 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 between the 

 two observations. The following Table contains the record of a 

 series of such measurements. As in the last case, the motion 

 of the pile is measured by turns of the handle, and the values 

 of the deflections are given with reference to a maximum of 100. 



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



Calorific intensity 

 Movement of pile. in lOOths of the 



maximum. 



Maximum .... 100 



I One turn towards visible spectrum 94*4 



...... 65-5 



42-6 



„ „ (extreme red). 28*3 



200 



14-8 



Ill 



Two turns in the same direction (green entered). 7*4 



4*6 



..... 2-0 

 „ „ (pile in blue) . 0'9 



Pile brought back to maximum. 



Maximum 100 



One turn from visible spectrum 67*1 



41-0 



23-0 



..... 13-0 



33 33 "'"* 



Two turns 5 - 



8-4 



0-0 



More than a dozen series of such measurements were executed, 

 each series giving its own curve. On superposing the different 

 curves, however, a very close agreement was found to exist be- 



