REMARKS ON COMBUSTION. 11 



phenomena which have not hitherto been claflified, nor exa- 

 mined with that precifion to which they are entitled. 



1 . Though the French chemifts have lately given the term The French 

 combustion a new meaning, and made it ftand for the general '™ ^(lion to™ 

 combination of a body with oxigen, I mean, for reafons which the aft of oxi- 

 will appear hereafter, to employ it in the fenfe ufually affixed genation. 

 to the term by the generality of mankind. Now w T hen a 

 body undergoes combuftion, in the common fenfe of the 

 word, two things always take place. 1 . The body gradu- Ufual aceepta- 

 ally waftes away, and often difappears altogether j it is then p™ f °f r ^ ** r ™ 

 faid to be confumed or burnt. 2. During the whole of this f um j,tion or wafte 

 procefs it emits heat and light ; the heat and light thus emitted jwg beat and 

 are ufually denominated fire, and the wafte of the body is 

 considered as the eftecft or confequence of its combuftion. If 

 either of thefe two phenomena be wanting, we do not fay in 

 common language that a body is undergoing combuftion, or 

 that it is burning. Every theory of combuftion then muft ex- The theory muft 

 plain, 1. Why the burning body is wafted and altered. 2. explain thefe 

 Why during the progrefs of this alteration heat and light are 

 emitted. 



2. If we take a view of the different bodies which occupy Relative to com- 

 the attention of chemifts, we fliall find, that as far as com- buftion bo *» 



» n- i , t 1 1 1 3re 1# SOflWOl- 



buftion is concerned, they may be arranged under three tibles, orz.fup- 

 claffes; namely, 1. Combuftibles. 2. Supporters of com- porters of com- 



i n- „ t i n-i i buftion, or 3. 



bullion. 3. Incombuftibles. incombuftible. 



I. The combustibles are thofe bodies, which are faid in 1. Combuftibles 

 common language to barn. During combuftion they appear or th ; e bodies 

 to emit light and heat, and at the fame time gradually wafte 

 away. When this change has reached its maximum, the 

 procefs of combuftion is at an end. The clafs of combuftibles / 

 is very numerous ; but all the bodies belonging to it may be 

 fubdivided into three fets ; namely, 



1 . Simple combuftibles, 



2. Compound combuftibles, 



3. Combuftible oxides. 



The fimple combuftibles are twenty-four or twenty-five in ^^ are fim . 

 number, namely, combuftibles j or 



1. Sulphur, 3. Carbon, 



2. Phofphorus, 4. Hidrogen gas, 

 5. All the metals *. 



* Except perhaps gold, filver, and mercury. 



The 



