76 



Spontaneous combustion of antimony or arsenic may be citetl 

 as an instance. To proceed a step further, -vve may have light 

 produced actually imder water, as in the action of sulphuric acid, 

 phosphorus, and potassic chlorate. In these experiments, however, 

 we have not been producing light and ilame without something to 

 Inirn, neither is it possible for man to do this. One tiling, how- 

 ever, he may do, and that is to carry on his burning at one place 

 and produce the resultant light and heat in another. As an 

 instance of this may be mentioned the electric light. Our burning 

 is carried on in our battery, wherevei' that may be, and we have 

 the resulting effects before us on the table. This light requires 

 no air for its support, and may be shown untler water, and further, 

 may be shown in a vacuum, lij' means of a liuhmkorf's coil and 

 prepared vacumn tubes. 



Ordinarily light and flame are associated together in oiu- ideas : 

 this is not necessarily the case. We may have h'ght without flame, 

 and indeed some of our most intense lights are of this nature. 

 Iron burns in oxygen with brilliant corruscatious, yet here we have 

 no flame. Flame is produced when a gas is burning ; when, how- 

 ever, a solid is burnt we have merely a glow. Xeither are light 

 and heat necessary companions in similar proi)ortions. Intense 

 heat is produced liy the combustion of hydrogen and oxygen. 

 AVe have, however, lint little light ; on now introducing some solid 

 matter as lime we get a light almost too brilUaut to be looked at. 

 It is self-evident that the heat must thus have been lowered. The 

 denser a body the greater the light evolved liy it at tlie same 

 temjierature. Tyndall's researches on Sjjectrum Analj-sis have 

 shoAvn that the majority of the heat rays of the sun, &:c., are im. 

 accompanied hy light. One or two other peculiar properties of 

 ilame must no\\' l)e mentioned. Flames may be made the source 

 of musical sounds : a jet of hydrogen biirned in a glass tube gives 

 a clear musical note. Flame may not only l)e thus utilized as a 

 source of sound, Imt it also possesses another more wonderful 

 property. Under certain conditions it "hears" sound, that is in 

 its OA\-n peculiar manner. A flame liurning from a pinhole jet 



