Management of Light in Illumination. 163 



burner (about half an Inch in length) to be made of 

 silver instead of tin or copper ; and, as this alteration 

 does not occasion an additional expense of more than 

 eighteen pence or two shillings, it must in the end turn 

 out to be very economical. All lamps with vertical 

 burners should be constructed in this manner, espe- 

 cially when they are destined to be used with purified 

 oil. 



As I am persuaded that this portable lamp will be 

 found useful, I am anxious that all its essential parts 

 may be so particularly described as to leave no doubt 

 or uncertainty respecting its construction ; for unless 

 this be done all my labour will be to little purpose. 



Fig. 4, Plate VIII., shows the manner in which the 

 upper part of the lamp is fixed to its stand. <5 is a 

 part of the vertical tube, which is surrounded at its 

 upper extremity by the circular reservoir ; c is the 

 upper part of the column which serves as a stand for 

 the lamp ; k is the hoop which serves to mask the air- 

 holes (represented in Fig. 3 by dotted lines), through 

 which the air passes into the tube b. This hoop is 

 attached to the vertical tube b by means of three ver- 

 tical wires, which are soldered to the tube. Two of 

 them are represented in this figure. One of them, 

 V, descends lower than the under side of the hoop 

 which it supports; and its lower extremity is turned 

 inwards, and forms a hook. The two others descend 

 each about one tenth of an inch below the lower side 

 of the hoop, but they are not bent, i is the ring of 

 wire which forms the moulding at the upper extremity 

 of the stand of the lamp. This moulding is inter- 

 rupted in one part of it, as is clearly shown in the 

 figure. 



