io6 Mr. Morgan's Obfervations and Experiments on 



The moil fingular phaenomenoii attending a burning body 

 is, perhaps, the red appearance it aflumes in its laft ftage o£ 

 combuflion. The preceding facls and obfervations may, I 

 think, help ns to exphiin it.. 



1. After a body has continued to burn for forae time, its 

 external furface. is to. be regarded as having loH: a great portion. 

 if not the whole of thofe rays which the firft application of 

 iieat was able to feparate. But thefe rays were the indigo, the 

 violet, the blue, and perhaps the green. Nothing, therefore, will 

 remain to be feparated, but the yellow, the orange, and the red, 

 Confequently, the combuftion of the body,, in its laft ftate of de- 

 compofition, can affume no other than a reddifh appearance. But 



2. Let us confider the external furface of the combuflible 

 as annexed to an inner furface, v/hich may be partly, but not fo 

 perfectly decompofed as itfelf : for the violence of the heat will 

 be found to leiien in its effeds the nearer it approaches to the 

 center of the fubftance which is expofed to it. Hence we are 

 to confider the parts v/hich are jufi: covered by the external fur- 

 face as having loft lefs of their component light than the exter- 

 nal furface itfelf. Or the former may retain the green rays 

 when the latter has loft both indigo, violet, blue, and green. 



3. Thofe parts which are nearer the center of the body 

 than either of the preceding muft, as they are further from 

 the greateft violence of the heat, have lofl: proportionably 

 fewer of their rays. Or while the more external parts may 

 have lofl all but the red, thefe may have loft only the indigo 

 and violet. 



4. The moft central parts may be unaftecled by the heat ; 

 and whenever the fire does reach thefe parts, they will imme- 

 diatsly difcharge their indigo rays, and be decompofed in the 



gradual 



