INVESTIGATIONS RELATIVE TO ILLUMINATING MATERIALS 497 



All fatty oils absorb oxygen, wbicli unites with them to form oxides 

 of their combustible ingredients; oil therefore freely exposed to the air, 

 must in time gradually diminisli in its power of combustion. It should 

 not, therefore, be open to the atmosphere when the oil is to be stored, 

 but covered Avith a thin wooden plane, which floats upon the surface of 

 the oil, and thus in a great measure excludes the air. The freezing of 

 lard-oil does not appear to aflect its quality. 



Considerable difficulty was experienced in the introduction of lard- 

 oil, on account of the objection to it on the part of the keepers ; in some 

 cases from the want of exjierience in using it, and in others from the in- 

 terference of venders of sperm-oil. This difficulty however was obvi- 

 ated by a resolution of the board, by which any keeper that declared 

 his inability to burn lard-oil should be requested to resign, since it had 

 been abundantly proved that this oil, with proper management, could 

 be made favorably to compete with sperm. Its introduction was a mat- 

 ter of great importance in an economical point of view ; it saved the gov- 

 ernment $100,000 annually for several years. 



Another important step in the introduction of lard-oil was that of fur- 

 nishing a lamp wliich would burn it with the greatest perfection. This 

 was due to the invention of Mr. Joseph Func^k, foreman of the lamp- 

 shop. As we have said, in order to burn lard-oil it is necessary it 

 should be kept at a high temperature, and for this purpose the heat of 

 the draught of the lamp was passed through the center of the reservoir. 



Previous to the change in the illuminating material there had been 

 used in the Light-House Establishment three classes of lamps, viz, the 

 mechanical lamp for the first, second, and third orders, and the moder- 

 ator and fountain lamps for the fourth, fifth, and sixth orders. 



In the mechanical lamp the oil was placed in a reservoir below the 

 burner, and pumped up by means of clock-work. This apparatus is of a 

 complicated character, and is subject to derangement. The valves must 

 be renewed from time to time, and the clock-work cleaned. The i)roper 

 performance of these operations is beyond the skill of an ordinary keeper, 

 and requires the frequent aid of a trained lampist. 



The moderator lanlp is less complicated, and was invented to obviate 

 the difficulties just mentioned. In this the oil is elevated by the des(;eut 

 of a heavy piston, and forced up through a small conical hole, the flow 

 being regulated by the conical end of a wire, which is gradually with 

 drawn as the weight descends, so as to give a less-obstructed flow as 

 the hydrostatic pressure of the oil increases. From this arrangement 

 it takes its name of moderator lamp. This apparatus however is liable 

 to irregularity on account of derangement of the sitpplying apparatus, 

 the varying friction of the packing of the piston, as well as the change 

 in the flow of the quantity of oil, owing to its less liquidity due to a dimi- 

 nution in temperature. 



The reservoir of the fountain-lamp consists in an air-fight vessel, 

 usually cylindrical, from the bottom of which descends a tube, terminat- 

 S. Mis. 31 32 



