1843.] On the Ventilation of Lighthouse Lamps. 363 



If the chamber or lantern be not perfectly ventilated, the sub- 

 stances produced by combustion are diffused through the air, 

 so that in winter or damp weather the water condenses on the 

 cold glass windows, which, if the light be a fixed one, greatly 

 impairs its brilliancy and efficiency, or, if the light be a revolving 

 one, tends to confound the bright and dark periods together. 

 The extent to which this may go, may be conceived, when it 

 is considered that some lighthouses burn as much as twenty, 

 or more, pints of oil in one winter's night, in a space of 12 or 

 14 feet diameter, and from 8 to 10 feet high, and that each pint 

 of oil produces more than a pint of water ; or, from this fact, 

 that the ice on the glass within, derived from this source, has 

 been found in some instances an eighth, and even a sixth of an 

 inch in thickness, and required to be scraped off with knives. 



The carbonic acid makes the air unwholesome, but it is easily 

 removed by any arrangement which carries off the water as 

 vapour. One pound of oil in combustion produces about 1*06 

 pound of water and 2'86 pounds of carbonic acid. 



The author's plan is to ventilate the lamps themselves by fit 

 flues, and then the air inside the lantern will always be as pure 

 as the external air, yet with closed doors and windows, a calm 

 lantern, and a bright glass. 



In lighthouses there are certain conditions to which the 

 ventilating arrangement must itself submit, and if these are not 

 conformed with, the plan would be discarded, however perfect 

 its own particular effect might be. These conditions are chiefly, 

 that it should not alter the burning of the oil, or charring of 

 the wicks, that it should not interfere with the cleaning, 

 trimming, and practice of the lamps and reflectors, that it 

 should not obstruct the light from the reflectors, that it should 

 not, in any sudden gust or tempest, cause a downward blast or 

 impulse on the flame of the lamp, that, if thrown out of action 

 suddenly, it should not alter the burning ; and, added to these, 

 that it should perform its own ventilating functions perfectly. 



Lighthouses have either one large central lamp, the outer 

 wick of which is sometimes 3| inches in diameter, or many single 

 Argand burners, each with its own parabolic reflector. The 

 former is a fixed lamp ; the latter are frequently in motion. 

 The former requires the simplest ventilating system, which 

 may be thus described : 



