132 HEATING. 



are points demanding the most attentive consideration from all 

 who are interested in these matters. 



Much confusion at present prevails in all that regards hot- 

 house furnaces, as well in their practical working as regards the 

 admission of air and the combustion of fuel. In commenting 

 briefly upon the constituents of coal smoke, or coal gas, car- 

 buretted hydrogen, and the quantity of air required for their 

 combustion, we will be as explicit as possible, without going 

 more into scientific detail than is consistent with the means and 

 opportunities of that class of practical men for whom we write. 



3. The first step towards effecting the perfect combustion of any 

 combustible gas, is the ascertaining the quantity of oxygen with 

 which it will chemically combine, and the quantity of air re- 

 quired for supplying such quantity of oxygen. Here, then, we 

 are called on for strict chemical proofs these several quantities 

 depending, not on the dictum of any chemist, but on the faculty 

 which each particular gas possesses of combining with certain 

 definite proportions of the other the supporter ; these respec- 

 tive proportions being termed " equivalents" or combining vol- 

 umes. This doctrine of equivalents must, therefore, be under- 

 stood before we can be prepared to admit the necessity of any 

 precise quantities. This question, as to quantity, is also the 

 more important when we consider that the quantity of effective 

 heat obtained by the combustion of any body, will be in exact 

 relation to the quantity of oxygen with which it will chemically 

 combine. 



Let us begin, then, by inquiring into the constitution of the 

 coal gas, and the relative proportions in which its constituent 

 elements are combined, as these necessarily govern the propor- 

 tions in which it will combine with the oxygen of the air. 



Now, the doctrine of " equivalents," that all-convincing proof 

 of the truths of chemistry, being clearly defined and understood, 

 reduces, to a mere matter of calculation, that which would 

 otherwise be a complicated tissue of uncertainties. And let no 

 mechanic feel alarmed at this introduction to " elementary atoms " 

 and " chemical equivalents," or imagine it will demand a deeper 

 knowledge of chemistry than is compatible with his sources of 



