DISCOURSE OF W. B. TAyLoR. 309 



When the steadily advancing cost of whale oil made it necessary 

 to seek for some more economical illuminant, he attacked the prob- 

 lem with his habit of scientific method. Colza oil or rape-seed oil 

 had been used in France with some success; and efforts were made 

 to introduce its culture and production in this country. Lard oil 

 had been tested by Professor J. II. Alexander of Baltimore, and 

 pronounced by him of very inferior value as an illuminant. For 

 accuracy of determination, Henry caused to be prepared at the 

 Light-house Depot on Staten Island, a long dark fire-proof cham- 

 ber, and had it painted black on all its interior surfaces for the 

 purpose of photometric observations. In ordinary lamps, the colza 

 oil was found to be about equal to whale oil in illuminating power, 

 and lard oil inferior to it. Petroleum or mineral oil was also tried ; 

 but its quality was at that time too variable, and its use was found 

 to be too dangerous. Experiment showed that lard oil had a 

 greater specific gravity than sperm oil, a less capillarity or ascen- 

 sional attraction in a wick, and a less perfect fluidity. The con- 

 ditions were varied; and it was found that with elevation of 

 temperature, the fluidity, and the capillarity, of the lard oil 

 increased more rapidly than those of the sperm oil, until at about 

 250° F. the former surpassed the latter in these qualities. With 

 these results, it became important to compare the oils in large 

 lamps, such as were actually required for the lanterns of light- 

 liouses. The heat evolved by the large-sized Argand burners, 

 would seem peculiarly to favor the lard oil : a few trials, with a 

 proper adaptation of the lamps, established its supremacy; and 

 conclusively demonstrated — contrary to all the laboratory trials of 

 former experimenters, that for the purpose desired, this contemned 

 article was for equal quantities a more brilliant illuminant than 

 mineral kerosene oil, or vegetable colza oil, or animal sperm oil, 

 while its market price was only about one-fourth that of the latter.* 

 Against all the opposition of interested dealers, and prejudiced keep- 

 ers, the lard oil was at once introduced into actual use in the years 

 1866 and 1866, in all the light-houses of the United States; with 

 a saving of at least one dollar on every gallon of the hundred 

 thousand in annual use; that is of 100,000 dollars per annum. 



♦See "Supplement," Note N. 



