102 



OPTICAL PROJECTION 



of sheet-iron (fig. 57). In the better class this is enclosed 

 rather loosely in a wooden case. Such lanterns are usually 



worked (with oil) 

 very near the 

 screen, a combi- 

 nation-lens of 4J 

 inches focus being 

 most usual. As 

 regards thus using 

 a single lantern 

 with an oil-lamp, 

 nothing need be 

 added to what 

 has been said in 

 Chapter III., ex- 

 cept that all the 

 lenses will, of 



Fio.57.-Iron Lantern <JOUrse, ^ Bright 



and clean, or, if 



not so, will be fresh wiped with a wash-leather, kept for 

 that purpose alone in a collar-box, or something of that 

 kind, and religiously preserved from grease. A wash-leather 

 once greased anywhere, is of no further use until washed. 

 The lamp is fitted to its proper place, and it only has to be 

 trimmed and attended to, and the slides properly focussed 

 with the rack and pinion. 



When such a lantern is used with a tray and jet instead 

 of the lamp, again all the needful directions for the manage- 

 ment of the light have been given in Chapter IV., but it will 

 be necessary now to carefully centre and adjust the light in 

 the manner described under 62. 



A single lantern made for limelight only, however, ig 

 generally constructed differently. The body itself is made of 

 mahogany, and it is the lining of sheet-iron or tin which is 

 attached to this : there is usually an all-brass front, with a 



