170 ILLUMINATION. [VI. 



these metliods, the flame as it issues from a jet may be directed 

 upon a wick of fine platinum wire, whose incandescence will 

 produce the desired illuminating effect. Another method is 

 to naphthalize the hydrogen, i. e. to pass it through a liquid 

 or over a solid hydrocarbon (such as naphtha or naphthalin), 

 or to mix it with the vapor of a hydrocarbon, in all which 

 cases its illuminating property depends on the same causes as 

 in all ordinary cases of combustion for light, viz. the inflamma- 

 tion of hydrogen and the precipitation and momentary in- 

 candescence of carbon in the flame. 



2. Burning-fluids. — These are generally solutions of cam- 

 phine (purified spirit of terpentine) in alcohol, and are burned 

 in lamps constructed for the purpose. Their danger has 

 been pointed out from year to year by one of the writers, in 

 public lectures delivered in the Franklin Institute, in Phila- 

 delphia ; yet such is the neatness of these illuminating liquids, 

 their convenience and brilliancy, that they continue to be 

 used until a serious accident awakens the public to a sense of 

 their danger. But the disaster serves only to deter those from 

 their use who were more immediately affected by it. There 

 is no doubt that burning-fluids may be safely used by those 

 who understand the conditions of their explosiveness, or who 

 exercise care in their use ; but since their tendency to explo- 

 sion cannot be prevented, and since knowledge and care will 

 not generally attend their use by the public, they should be 

 abandoned. 



Let us not however abandon the idea of finding a liquid 

 which shall possess the requisite qualities of cleanliness, cheap- 

 ness, illumination, and freedom from danger. Sperm-oil pos- 

 sesses the last two qualities ; burning fluids the first three ; 

 lard-oil is cheap and free from danger, but is not cleanly, is 

 too liable to congeal in winter, and is apt to clog the wick. 

 Naphtha is very little, if at all, liable to explosion, but it 

 contains an excess of carbon, and it is too apt to smoke when 

 burned in an ordinary lamp. Since sperm-oil has a high 

 illuminating power and is free from danger, we may yet hope 

 to discover a liquid which shall possess these properties to- 



