90 Prof. Draper on the Nature of Flame, 



mainly a difference of definition, while some influence is to be ascribed 

 to that daring hopefulness in investigation to which the world is so 

 deeply indebted, and which causes its possessor to see possibilities 

 of scientific conquest where others see none. — Ed.] 



XIII. On the Nature of Flame, and on the Condition of the Sun's 

 Surface. By John W. Draper, M.D., Professor (f Che- 

 mistry and Physiology in the University of New lorA:*. 



AMONG the recent publications on photo-chemistry, there is 

 one by Professor Dove on the Electric Light (Phil. Mag. 

 Nov. 1857), which will doubtless attract the attention of those 

 interested in that branch of science. Examination by the prism, 

 and by absorbing and reflecting coloured bodies, leads him to 

 the conclusion that it is necessary to consider the luminous 

 appearance as having two distinct sources : — ]st, the ignition or 

 incandescence of the material particles bodily passing in the 

 course of the discharge ; 2ndly, the proper electrical light itself. 

 As respects the first, he illustrates its method of increase from 

 low to high temperatures, by supposing a screen to be with- 

 drawn from the red end of the spectrum through the coloured 

 spaces successively towards the violet ; and that of the latter from 

 the bluish brush to the bright Lcyden sparks, by a like screen 

 drawn from the violet towards the red. 



The true electric light exhibits properties resembling those 

 observed in actual combustions, as though there was an oxida- 

 tion of a portion of the translated matter when the spark is 

 taken in air. The order of evolution of rays in this instance 

 happens to be the same as in the second illustration of Professor 

 Dove, that is, from the violet to the red. There are certain facts 

 connected with these appearances of colour which are not gene- 

 rally known, and deserve to be pointed out. 



In the Philosophical Magazine (Feb. 1848), I showed experi- 

 mentally that there is a relation between the colour of a iiamc 

 and the energy with which the combustion giving rise to it is 

 going on. The more vigorous and complete the combustion, the 

 higher the refrangibility of the light. A flame bm-ning in its 

 most tardy and restricted way, emits rays that are red ; but 

 burning in its most complete and effective manner, rays that are 

 violet. In intermediate states of combustion, the intermediate 

 colours are evolved in their proper order of refrangibility. 



The flame of a candle or lamp consists of a series of concen- 

 tric luminous shells, surrounding a central dark core. These 

 shells shine with different colours, the innermost one imme- 

 diately in contact with the dark core being red, and having a 

 temperature of 977° P. Upon this, in their proper order of 

 * Communicated by the Author. 



