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Petroleum is the most economical of all known sources of 

 light. And when we take into account, too, the inexpensive 

 character of the apparatus with which it is burned, the 

 safety and cleanliness of its use, the possibility of using it 

 as well in country as in town, our appreciation of it as a 

 source of illuminating power is greatly enhanced. 



The chief difference between the apparatus required to 

 burn this as compared with sperm oil is the necessity of a 

 chimney. This arises from the smoke given off by the 

 Petroleum when burned in the free air. A higher tempera- 

 ture is required to burn the carbon particles than can be ob- 

 tained in a flame exposed to the air. This is secured by 

 surrounding the flame with a glass chimney, which has both 

 the effect of increasing the temperature and furnishing 

 by means of the draft of the chimney a better supply of 

 air. The wick used is generally the flat wick, and with this 

 a sufficiently large flame can be obtained, but when a still 

 larger flame is required the argand wick with the chimney 

 would effect it. The chimney has in some newer contri- 

 vances for burning this oil been dispensed with. This is 

 done by surrounding the base of the flame with a metal 

 chimney, and suffering the flame to be burned through a slit 

 in the top of the metal. The necessary current of air is 

 thus drawn past the sides of the flame and the combustion 

 is nearly perfect. But although this contrivance avoids the 

 expensive use of chimneys, and renders the lamp more por- 

 table, yet the facts that the combustion is less perfect, the 

 flame less brilliant, and the odor more perceptible, will pre- 

 vent its universal adoption. 



VII. Explosibility. — Much uncertainty and consequent 

 anxiety exist in public opinion in regard to the liability to 

 explosion in Petroleum. Insurance companies, both in this 

 country and in England have been much exercised in regard 

 to the risks upon this material. Even scientific authorities 

 to whom appeal has been made in the premises have not 



