AN ACCOUNT OF INVESTIGATIONS RELATIVE TO ILLUMINAT- 

 ING MATERIALS.* 



By Joseph Henry. 



It has been the policy of the Light-House Board siuce its first estab- 

 lishment not only to adopt the latest improvemente which have been 

 made in other countries, but also to add by original investigations to 

 the sum of knowledge on aids to navigation. In accordance with this 

 policy, the Board has endeavored to keep itself informed as to the prog- 

 ress of the light-house systems of other countries, and in the erection 

 of new towers and the supply of new apparatus to adojit those imi^rove- 

 ments which have from actual experience been preferred 5 and, further- 

 more, the committee on experiments have devoted a iiortion of ever}' 

 year to investigations which might develop new facts tending to greater 

 economy or efficiency in the various ai^pliances by which the dangers of 

 na%dgation are diminished. 



At the commencement of the operations of the Light-House Board, in 

 1852, sperm-oil was generally employed for the purpose of illumination. 

 This was an excellent illuminant, but as its price continued to advance 

 from year to year, it was thought proper to attempt the introduction of 

 some other material. The first attempt of this kind was that of the in- 

 troduction of colza-oil, which was generally used in the light-houses of 

 Europe, and is extracted from the seed of a species of wild cabbage, 

 known in this country as rape, and in France as colza. For this pur- 

 pose a quantity of rape-seed was imported from France and distributed 

 through the agricultural department of the Patent-Office to different 

 parts of the country, with the hope that our farmers might be induced 

 to attempt its cultivation. Although the climate of the country ap- 

 peared favorable to its growth, and special instructions were prepared 

 and distributed by the Light-House Board for its culture and the means 

 of producing oil from it, yet the enterprise was not undertaken with 

 any approximation to success, except in Wisconsin, where a manufactory 

 of rai)e-seed oil was established by Col. C. S. Hamilton, formerly of the 



[*From the Report of the U. S. Light-House Board for 1875. The researches de- 

 scribed in this memoir have a sufficient scientific vahie and popular interest to fully 

 justify their reproduction here. — S. F. Baird.] 



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