174 ANNUAL OF SCIENTIFIC DISCOVERY. 



to a system of bulbs, through which are driven the air in which 

 the gas has burned and the liquid used to wash it. From the 

 bulbs they pass into a two-necked receiver placed over the cylin- 

 der, whence the air escapes into the aspirator, while the liquid de- 

 scends through a small tube to the bottom of the cylinder and 

 repeats its course. The liquid used is an ammoniacal solution of 

 copper, the ammonia serving to fix the sulphur compounds, 

 while the copper determines, in presence of an excess of air, the 

 oxidation of sulphite to sulphate." The air which enters the ap- 

 paratus is freed from sulphur compounds by being passed through 

 an ammoniacal solution of copper. When about 2 cubic feet 

 of gas have been consumed the liquor is drawn off, the apparatus 

 rinsed with water, and the sulphur precipitated as sulphate of 

 barium after the excess of ammonia has been driven off. Lond. 

 Jour, of Gas-Lighting. 



Various Formulce proposed for the Relation between the Quantity 

 of Light produced and the Amount of Gas consumed. Fred. E. 

 Stimpson. The author found upon examination that three for- 

 muloe had been proposed for this reduction, namely : 



(1) The common one 



1 L 

 V 0" 



which is expressed by saying that the quantity of light, Z, is pro- 

 portional to the quantity of gas, g, consumed ; (2) that produced 

 and used by Bunsen and Roscoe, Phil. Trans., CXLIX. (1859), 

 page 884, 



I I' g g' 



V^T" ~ </-</" 



which is expressed by saying that for a given burner the increase 

 of light is proportional to the increase of the quantity of gas con- 

 sumed ; (3) "Farmer's Formula," proposed by Professor Silli- 

 man at the Salem Meeting of the American Association, 



L= ^ 



V ' g>* 



which is expressed by saying that the light is proportional to the 

 square of the consumption. These three formulas, transposed 

 so as to express the value of I, become, 



V 

 ! l ~ ~ or l 



(3.) I = - or I = Ag*. 

 y 



Mr. Stimpson had collected from various publications upwards 

 of 120 independent series of determinations of the relative illu- 

 minating power of gas consumed at various rates from different 

 burners. These burners comprised single jet, union jet, or 

 fish-tail, slit or bat's-wing, and argand ; each set contained from 2 

 to 10 single determinations. These series, together with some of 



