1C75] WRITINGS OF JOSEPH HENRY. 501 



and required no trimming during the night; it burned well 

 for several nights, and the keeper congratulated himself on 

 fhe success of what he considered a very important experi- 

 ment. Unfortunately however on the last morning that the 

 lamp was used he attempted to put it out in the usual way 

 by blowing the air from his lungs down the chimney, when 

 an explosion took place, which scattered the oil in a burning 

 state over the deck of the tower and also on his clothes. In 

 his fright he ran down the stairs of the tower, and had 

 scarcely reached the ground when a violent explosion was 

 heard above, which blew off the whole lantern and broke the 

 lenticular apparatus. 



The explanation of these two explosions is not difficult. 

 The burning of the oil during the night left a space void of 

 the liquid in the reservoir of the lamp which was filled with 

 air and vapor, which happened on this occasion to be near 

 the explosive proportions; on blowing air down the chimney 

 it mingled with the vapor, furnishing the quantity neces- 

 sary for the violent combination, and consequently the 

 explosion occurred which broke the lamp. The second 

 explosion was caused by the ascent of the vapor from the 

 burning oil on the deck, and took place when the quantity 

 exhaled amounted to a tenth part of the volume of air pres- 

 ent. The two then suddenly rushed into combination, pro- 

 ducing the effects that we have mentioned. 



Under favorable circumstances, this lamp lighted with 

 kerosene might have burned silently for several weeks, but 

 in accordance with the doctrine of chances, time enough 

 being given, an explosion was inevitable. Facts of this kind 

 in connection with the difficulty experienced in burning 

 mineral oil in light-house lamps, induced the Light-House 

 Board to adopt lard oil. 



Various experiments have been made from time to time 

 by the Light-House Board with a view to the introduction 

 of petroleum as an illuminating material, as soon as oil 

 could be obtained in this country of a suitable character, 

 lard oil having advanced in price to such a degree as 



