REFLEXION OF LIGHT. 441 



such, for instance, as the effect of annealing might produce, 

 or the burning off from it of films of moisture, or of oxidable 

 substances. 



The general result of these experiments is, that no differ- 

 ence is perceptible by the eye in light reflected by a polished 

 surface, whether that surface is ignited or not ; that the 

 superficial molecular uniformity, which causes a bundle of 

 parallel rays to preserve their parallelism of direction when 

 reflected, is, if the ignited substance be inoxidable, not broken 

 up by ignition. 



I know of no photometer which would be suitable for indi- 

 cating their effects with greater accuracy than the eye ; but, 

 although these results lead to a conclusion different, I believe, 

 from that which would have been arrived at a priori, they by 

 no means exclude the possibility or even probability of some 

 difference being produced in the direction or character of light 

 reflected from ignited surfaces as compared with that reflected 

 from unignited surfaces. 



The fixed lines in the spectrum, for instance, differ mate- 

 rially according to the source of light ; and even supposing 

 the ignited surface to make no difference in the character or 

 position of the fixed lines of reflected solar light, a point which 

 I have no apparatus sufficiently delicate to detect, yet there 

 is every probability of novel and valuable results being attained 

 by the interference of this light of incandescence with that of 

 solar or other light reflected from the incandescent body, the 

 same body being then, in some sense, the source of two dif- 

 ferent descriptions of light, which differences are capable of 

 detection by the different position and character of the fixed 

 lines in their respective spectra. Such experiments, and many 

 others which they obviously suggest, appear to me to offer 

 an Interesting field of experiments in physical optics ; and to 

 those who are more practically acquainted with this science 

 than I can pretend to be, and who may possess more delicate 

 means of detecting minute effects, I therefore leave them. 



