478 WRITINGS OF JOSEPH HENRY. [1875 



proximation to success, except in Wisconsin, where a manu- 

 factory of rape-seed oil was established by Col. C. S. Hamil- 

 ton, formerly of the United States Army. To this manu- 

 factory the Light-House Board gave special encouragement, 

 and purchased at a liberal price — all the oil that could be 

 supplied : the quantity however which could be procured 

 was but a small part of the illuminating material required 

 by the annual consumption of the Light-House establish- 

 ment. 



The price of sperm oil still continuing to increase, the 

 Board employed Prof J. H. Alexander, a chemist of Balti- 

 more, to make a series of investigations on different oils, to 

 ascertain a method of detecting adulterations in them, and 

 to determine the relative economical value of different kinds 

 of oil which might serve for use in light-houses. In his 

 report Prof. Alexander recommended — as a means of de- 

 tecting adulterations in oil, a thermal test based upon the 

 amount of heat evolved by mixing a given quantity of the 

 oil with sulphuric acid of a given specific gravity, and 

 noting the rise of temperature as indicated by a standard 

 thermometer in a unit of time. For using this method, it 

 was proposed to ascertain by actual experiment — the heat 

 evolved by mixing pure oils with a given quantity of acid, 

 and afterward oils adulterated with given quantities of lard 

 or inferior oils. This ingenious suggestion was however 

 never reduced to practice. The method was too refined ; 

 the difference of heat evolved was scarcely sufficient to be 

 noted unless great precautions were taken to prevent loss by 

 radiation and conduction, and consequently it could not be 

 employed by ordinary inspectors. In regard to lard oil, 

 Prof Alexander — not having ascertained the best conditions 

 for burning it, consequently rated it very low in the scale of 

 economical value as a light-house illuminant. 



In this stage of the history of the subject, the chairman of 

 the committee on experiments commenced himself to inves- 

 tigate the qualities of different kinds of oil, and was soon led 

 to direct his attention to the comparative value of sperm 

 and lard oils. The experiments made by Prof. Alexander 



