436 On the Benefits that may he expected 



a number of experiments, of which T shall merely state the 

 results, and not the proceedings. The gas was prepared 

 from Welsh culm enclosed in a common iron pot covered 

 with a head made of brick ware ; the tubes for conducting 

 the gas were leaden pipes furnished with perforated roses like 

 the extremity of the pipe of a common watering-pot. In 

 this manner it was found that the degree of the illuminating 

 power of the coal gas differs according to the degree of heat 

 employed for its evolution. Coal exposed to a dull red heat, 

 just sufficient for the production of the gas, yielded a gaseou3 

 product, which exhibited much less brilliancy when burnt 

 than gas obtained during a temperature of a bright che-rry 

 redness. 



100 cubic inches of the former gas when made to burn 

 slowly from a small aperture under a gardener's" large glass 

 bell, connected with a stone barrel filled with oxygen gas, 

 required 259 cubic inches of oxygen for its complete com- 

 bustion. On removing the residual gas into a stone pan 

 containing a ley obtained from the ashes of brush-wood, 

 1 14 cubic inches of the gas vanished. 



100 cubic inches of coal gas obtained at a cherry red 

 heat, required for its combustion 312 cubic inches of oxygen 

 gas obtained from oxymuriate df potash. The volume of 

 gas, after having been agitated with a like alkaline ley, lost 

 1 17 cubic inches. Hence the light of this gas, or its inten- 

 sity, is probably in the ratio of the quantity of" oxygen 

 necessary for the combustion of the carburetted hydrogen. 

 An increased temperature produces a gas better adapted for 

 illumination than a gas; procured by a degree of heat merely 

 sufficient for its evolution. 



The gas obtained at a low temperature has a much stronger 

 odour than that produced during an increased temperature. 

 It contains a considerable portion of sulphuretted hydrogen ; 

 for on collecting a quantity of it in a gasometer made of two 

 puncheons, the one of which was painted with white lead 

 within,- and suffering the gas to stand in this apparatus, it 

 completely blackened the white paint of the wooden vessel. 

 The gas obtained at an increased temperature acted but 

 feebly on the oxide of lead. 



Utft 



