424 MEMORIAL OF JOSEPH HENRY. 



be burned at a high temperature ; and as this could be readily 

 obtained in the case of larger lamps, there appeared to be no 

 difficulty in its application. 



" The previous trials had been with small lamps with single solid 

 wicks instead of the Fresnel lamp with hollow burners. After 

 these preliminary experiments, two light-houses of the first order, 

 at Cape Ann, Massachusetts, separated by a distance of only 900 

 feet, were selected as affording excellent facilities for trying in 

 actual burning, the correctness of the conclusions which had pre- 

 viously been arrived at. One of these light-houses was supplied 

 with sperm and the other with lard oil, each lamp being so trimmed 

 as to exhibit its greatest capacity. It was found by photometrical 

 trial that the lamp supplied with lard, exceeded in intensity of 

 light that of the one furnished with sperm. The experiment was 

 continued for several months, and the relative volume of the two 

 materials carefully observed. The quantity of sperm burned dur-' 

 ing the continuance of the experiment, was to that of the lard, as 

 100 is to 104." * 



This remarkable success in elevating the disparaged lard oil to 

 the highest rank as an illuminant, was of course very damaging to 

 the new manufacture of colza oil ; and no more characteristic tribute 

 to the energetic skill of Henry could be offered, than that contained 

 in the following frank and manly letter by Colonel C. S. Hamilton, 

 the manufacturer, (who by special invitation had been present at 

 several competitive photometric trials,) addressed to the Naval Sec- 

 retary of the Light-House Board, Commodore Andrew A. Harwood : 



DU LAC, Wis. May 16, 1868. 



" DEAR COMMODORE : I must confess my great disappointment at 

 the result of the experiments at Staten Island. It is however not 

 really so much the failure of rape-seed oil, as the undeniable excel- 

 lence of lard oil as a burner. I am satisfied now that for self-heat- 

 ing lamps there is no oil that will bear comparison with lard, but I 

 am equally satisfied that no colza oil will yield a better result than 

 ours, under exactly the same tests. We have but one more experi- 

 ment to make with colza ; it is its extraction by chemical displace- 

 ment. If this fails we shall abandon the whole business. 



"If all things are put together, I think the following statement 

 will be allowed, to wit : Our colza oil of this year is equal to any 

 foreign colza. It is better than any we have heretofore made. It 

 is better than sperm, or any other burner, excepting only lard oil. 

 Our failure then is owing to the superior excellence of lard oil, 

 which under the persistent investigation of the Board, has been 



* Report of the Light-House Board for 1875, pp. 86-88. 



