492 



WRITINGS OF JOSEPH HENRY 



[1875 



capacity of ten thousand gallons. On each tank is a register, 

 consisting of a glass tube so divided as to give the contents 

 in hundreds of gallons. The oil is delivered in three install- 

 ments : The first on the 1st of Ma}^ the second on the 10th 

 of June, and the third on the 22d of July. The vault and 

 tanks were constructed under the direction of General Poe 

 while engineer secretary of the board, who took a lively 

 interest in the introduction of lard oil and in the preliminary 

 experiments for determining its quality. 



A photometer room was afterwards fitted up in the Smith- 

 sonian Institution, in which several series of investigations 

 were made in regard to the illuminating power of different 

 oils. At the same time a series of experiments was under- 

 taken relative to their chemical characters and conditions, in 

 which experiments the chairman was assisted by Prof. C. M. 

 Wetherill whose untimely death the science of this country 

 has been called to mourn. Among the investigations in the 

 laboratory, are those given in the following table, relative to 

 the expansions of different oils — intended to facilitate the 

 purchase, the measurements being made at different temper- 

 atures. To obviate the necessity of the correction for tem- 

 perature, the oil is now purchased by weight. The following 

 results may however be of value in the application of differ- 

 ent oils to light-house purposes : 



Experiments upon Light-House Oils. 



[Density and volume of oils (and water) at different temperatures.] 



