132 PRACTICAL LESSONS IN SCIENCE. 



formed called carbon monoxide. It is colorless, tasteless, odor- 

 less, but exceedingly poisonous when inhaled. We often hear of 

 deaths caused by coal gas, and the gas from a pan of smoulder- 

 ing charcoal is often the cause of suicidal death, especially in 

 France. In an open coal fire, before all the coal is fully ignited, 

 the pale blue flames flickering over the mass are burning moxideof 

 carbon. It is probably the cause of death in the cases mentioned. 



All forms of artificial light, except the electric light, are flames 

 due to the combustion of some gas. In the case of illuminating 

 gas, the source of the light is made and stored as gas, in the case 

 of oil, the wick is ignited and as the oil comes up by capillary at- 

 traction it is expanded into gas and burns as a flame, and so 

 with the candle. At first a flame seems a simple thing and illumi- 

 nation seems as simple as the flame, but when one attempts to 

 explain the phenomena, the simplicity vanishes. We have already 

 learned that the hydrogen flame, while intensely hot yields but 

 little light. If we pulverize a little charcoal and dust it into a flame 

 of hydrogen it gives out an intense light; or if the hydrogen flame 

 be turned upon a piece of lime or other refractory substance it is 

 soon heated to incandescence giving out intense light, which leads 

 us to suspect that an illuminating flame must contain some solid 

 incandescent substance which is the cause of the illumination. 



If we examine a flame, as of a candle, we find it conical in 

 shape, pale blue below, dark in the center and yellow at the sides 

 and at the apex. Put a piece of porcelain or any solid substance 

 into the flame and the coat of soot deposited indicates the pres- 

 ence of solids in the flame. Pass a piece of paper into the flame 

 just above the wick, hold it there a moment, then remove it, and 

 if skillfully done there will be a ring of burnt paper with a little 

 portion uncharred within it, which indicates that the outside of 

 the flame is hotter than the inside dark portion. The substances 

 used for illuminating flames, as gas, oils and fats are composed 

 largely of compounds of hydrogen and carbon. About the wick 

 of a lamp or candle or the opening of the gas jet the unburned 

 gas makes the cool dark center of the flame. The oxygen uniting 

 more readily with the hydrogen than with the carbon forms 



