1516 CONGRESSIONAL PROCEEDINGS. 
The adoption of the mineral oil as an illuminant has made it possible to use a 
burner which can continue lighted for three, five, and even eight days and nights 
without filling, trimming, or attention of any kind. Such burners have been made 
and many of them attached to pier heads, to piles, and to isolated beacons, inaccess- 
ible in heavy weather. With lard oil these lights could only have been maintained 
in light-houses arranged for keepers to live in them, as the lard-oil burners would 
grow dim and finally go out unless trimmed every few hours. The building of these 
light-houses would cost anywhere from $25,000 to $250,000 each, and each such light- 
house would require from three to five keepers. The three, five, or eight day burner 
mineral-oil lights are established at a cost of from $50 to $500 each, and one man 
with a rowboat can attend to as many as he can reach in his boat. 
Thus the adoption of mineral oil as an illuminant has made the establishment of 
isolated harbor, bay, and sound lights inexpensive where it was formerly costly, and 
hence practicable where they were formerly practically impossible. Many such 
lights have been established and many more will be, it is quite evident. 
There are some 1,400 post lights on the western rivers. The establishment of 
these lights has revolutionized steamboating and it has made it as safe for boats to 
run by night as by day. Before the rivers were lighted, boats had to cease running 
and anchor or tie up to the banks at night. These rivers could not have been lighted 
with lard oil. This magnificent system of river lights was born of Professor Henry’s 
discovery that mineral oil could be used for light-house illumination, and his experi- 
ments, which resulted in the inyention and manufacture in the Board’s shops of 
light-house lamps in which mineral oil could be burned. 
It should be remembered that this great service to the Government has been ren- 
dered since his death; that the experiments in relation to mineral oil were just com- 
pleted at his death; that this service and great saving still continues and will continue 
to increase with the extension of the light-house service. Should Congress feel 
inclined to acknowledge this great indebtedness, now is a fitting time, since the last 
of the light-houses are even now this very year coming into the use of the mineral 
oils. 
Of other services to the light-house system some idea may be had from an official 
letter! of the naval secretary to the Hon. Secretary of the Treasury, dated May 21, 
1878. 
The letter given was in answer to the question from the Hon. Secretary of the 
Treasury: 
“*State the number of years Professor Henry served as a member of the board, the 
number as chairman of the board, and what number of months or days in each year, 
on an average, he was employed for business of the Government.’’ 
For this time an appropriation of $10,000 was made at Professor Henry’s death, 
but this sum could not be considered a recompense for the great services of Professor 
Henry. 
The letter hardly gives correctly the amount of time given by Professor Henry to 
the light-house work. His visits to the establishment at Staten Island were frequent, 
and the experiments made there lasted sometimes two or three weeks. He always 
returned overcome by fatigue. The two series of experiments given are but speci- 
mens of many which resulted in equal benefit to the country and the Light-House 
Board. 
It is quite true that during his lifetime, for his great services, Professor Henry 
received no other payment than that which met the itemized accounts of traveling 
expenses. Many of the items of expense were not recorded. Professor Henry was 
always the poorer rather than the richer for the light-house work. 
1See p. 807 in 45th Congress. 
