384 THE POPULAR SCIENCE MONTHLY. 



Having now considered the three causes which may convert the 

 luminous flame of our common street-gas into a faint and so-called 

 " non-luminous " flame, we are prepared to trace the operation of these 

 causes in the Bunsen lamp. All the various forms of the Bunsen lamp 

 burn a mixture of gas and air. Now, the air is itself a mixture of four 

 parts of nitrogen with one part of oxygen. The nitrogen of the air 

 takes no part in the process of combustion, but simply passes unchanged 

 through the flame. It is plain that this nitrogen must act on the flame 

 in two ways. First, it must cool it, just as any cold substance passing 

 through the flame would cool it ; and, second, the nitrogen dilutes the 

 illuminating gas. The effect of both cooling and dilution, as we have 

 seen, is to make a flame " non-luminous." 



But one fifth of the air is oxygen ; and this also has two effects 

 upon the flame. It makes it hotter, and it also tends to burn up the 

 carbon of the illuminating gas at once, before it can make the flame 

 luminous. All these causes cooling, dilution and oxidation of the car- 

 bon are operative at once in the Bunsen lamp, and the effect that we 

 see is the resultant of all these forces. Probably the most important 

 of them are the cooling and dilution by the nitrogen ; for, if the burner 

 through which the gases issue is heated, the flame becomes luminous 



again. 



The Bunsen lamp takes various forms, according to the purpose for 

 which it is to be used. In some of these the gas burns on the top of 

 a piece of fine wire-gauze, after becoming mixed with the air below it. 

 This form of burner is a very common one. It differs in appearance 

 from the usual form of Bunsen lamp, but is essentially the same in 

 principle ; that is, it burns a mixture of gas and air, and gives a " non- 

 luminous " flame for the same reasons that the ordinary Bunsen lamp 

 does. 



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THE COLORADO DESERT. 



By JOSEFII F. JAMES. 



THERE is an old adage which says that Arizona was the last spot 

 on earth to be created ; that Yuma is the outpost of the nether 

 regions, and the hottest place in the world. Every one knows the 

 old story of the two soldiers who, while stationed at Fort Yuma, died, 

 and, going straight to Hades, returned in a short time for their 

 blankets ! Be that as it may, there can be no doubt that parts of 

 Southern California and Arizona are among the hottest regions of 

 the world. Neither the Desert of Gobi in Asia nor the Great Sahara 

 in Africa can be worse, in this respect, than their small relative, the 

 Colorado Desert, in California. A protracted journey of some four 

 weeks over this desert gave me an excellent chance to see it and its 



