Management of Light in Illumination. 145 



within doors, but when the lamp is exposed to the 

 wind in the open air it will stand in need of its protec- 

 tion ; and it is also very useful when the lamp is car- 

 ried about from place to place, to prevent its being 

 extinguished by sudden jerks. 



I shall now endeavour to describe every essential 

 part of this lamp, and one which, more than any other, 

 distinguishes it from all other lamps: this is its sec- 

 ondary reservoir. 



This is a rectangular flat tube, which projects hori- 

 zontally from one side of the circular reservoir already 

 described. It is 1.25 in width, 0.8 of an inch in depth, 

 and 6 inches in length, and it is closed at its farther 

 end. It serves at the same time as a secondary reser- 

 voir and as a handle for holding the lamp when it is 

 carried about from place to place. Instead of being 

 made of a prismatic form, it is frequently swelled out 

 at its sides and rounded off at its extremity (farthest 

 from the lamp) ; and it is always painted black and 

 japanned. This is done in order to give it the appear- 

 ance of being merely a handle. 



As there was not room to introduce it entire in 

 either of the Figs. 2 and 3, it is in both shown 

 broken off at the distance of about an inch and a half 

 from the circular reservoir. 



It is on the upper part of this secondary reservoir, 

 where it projects horizontally over the upper part of 

 the circular reservoir, that the opening is placed by 

 which this lamp is filled with oil ; and this opening is 

 closed by a perforated brass stopper k, on which a hol- 

 low cone is placed that serves to give a passage to the 

 air which enters the reservoir. 



In the Fig. 3 (Plate VII.) a vertical section through 



VOL. IV. 



