294 Sir J. Robison oh the best Method of 



domestic illumination, have been so well laid down by the 

 late Dr Tm-ner, and by Dr Christison, as well as by other 

 chemists, that it would be superfluous to enter at all on this 

 part of the subject in a paper, the object of which is to give such 

 practical directions for the proper construction and manage- 

 ment of gas-fitting8, as may lead workmen to give the re- 

 quisite forms and proportions to the parts, and may enable 

 the consumers to obtain the quantity of light they require, 

 from the smallest practicable expenditure of gas, and with 

 the least possible inconvenience from the products of its com- 

 bustion. 



It is very generally believed, by workmen and others, that 

 the more freely the current of air is admitted to an argand 

 burner, the better will be the light ; and hence the burners 

 and glass chimneys in ordinary use are made in such a way 

 as to favour this view. No practice, however, can be more 

 incorrect, or can lead to less economical results. An atten- 

 tive observation of what takes place will shew, that there is 

 only a certain jyroportion of air required for the favourable com- 

 bustion of a definite measure of gas. If more air than this due 

 proportion be allowed to pass up the chimney, the size of the 

 flame will be reduced, and the quantity of light diminished : 

 if, on the other hand, less than the due proportion be admit- 

 ted, the surface of the flame will be increased by elongation, 

 but it will become obscure, and the quantity of light will de- 

 crease, o\ving to the escape of particles of unconsumed carbon. 

 A simple experiment will exemplify this. If the flame of an 

 ordinary argand burner be reduced, by partially shutting the 

 cock, to about half an inch high, the hght will be pale and blue, 

 because the supply of air is too great for the small quantity of 

 gas which is issuing. If partial obstruction be given to the 

 access of air, by applying a handkerchief under the burner 

 and chimney, it will be found that the size of the flame and 

 the quantity of light emitted will increase until it arrive at a 

 maximum, when, by farther obstruction, the admission of air 

 will be reduced below the proportion required for the burning 

 of the carbon, and the light will diminish. 



It appeal's, therefore, that the proportionate size and shape 

 of the burners, and the diameter and height of the glass chim- 



