Page:Popular Science Monthly Volume 20.djvu/398

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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 carbon 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 "nonluminous" flame for the same reasons that the ordinary Bunsen lamp does.



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