128 Management of Light in Illumination. 



The illuminator must first be pulled down to a con- 

 venient height, or, if it be not suspended by pulleys, 

 steps must be used for getting up to it. The mov- 

 able chain must then be unhooked and laid aside, and 

 the upper part of the balloon or the dome taken 

 away. When this has been done, one of the screws 

 which close the passages for admitting air into the 

 reservoir must be a little raised, if this should not have 

 been done before. 



If it be a balloon illuminator, the under part of the 

 balloon is to be unhooked, in order that it may fall 

 down and hang suspended by the hinge by which it is 

 attached to the horizontal brass hoop which supports 

 the reservoir. 



The burners are then to be lighted, one after the 

 other, and their glass chimneys fixed in their places. 



As soon as all the wicks are well on fire, they are to 

 be shortened, by drawing them back into their cylin- 

 drical burners by means of their racks or endless 

 screws, till their flames are reduced so as to become 

 very short and almost on the point of being extin- 

 guished. This is absolutely necessary, in order to pre- 

 vent the upper half of the balloon or the dome from 

 being scorched and perhaps set on fire by the heat, 

 in being passed over the ends of the chimneys of the 

 burners, over which it must pass in order to its being 

 put down into its place. 



As soon as this upper half of the balloon or the 

 dome is in its place, the movable chain may again 

 be hooked to the arrow to which it belongs ; after 

 which the wicks may be raised, one after the other, till 

 the flames are brought to be of a proper height. When 

 this has been done, the under half of the balloon may 



