SOIOPTICON MANUAL. 33 



vent thefr getting out of place and scratching against 

 each other; also between G f and jfiT, and between the 

 condensing lenses. 



The cap J is removed and placed behind the chimney. 

 The whole is snugly packed in a box with stuffing, and 

 the cover fastened on with screws. These particulars 

 may be advantageously referred to in case of repacking 

 by the purchaser or borrower. 



RULES FOR OPERATING THE SCIOPTICO\. 



In unpacking a new instrument the parts must be 

 separated, to remove the packing papers. 



Dust them if necessary. 



For the lenses and reflector use a duster that is soft 

 and clean. 



"Warm and dry the condensing lenses if inclined to fog. 



Adjust I 1 , 6r, 6r', J, and the lenses, as seen in Fig. 15. 



Shut the extension front back to its place. 



Fill the lamp about two-thirds full with standard 

 kerosene oil. The fire test should be 110 at least; that 

 of Pratt's astral oil is 145. 



Avoid carelessly tilting the lamp when it is very full, 

 and so avoid the smell of oil evaporating from the out- 

 side surface. 



Turn down the wicks, so they will not rub against the 

 deflecting plate while withdrawing or inserting the lamp. 



It is convenient to stand the instrument so as to be 

 about breast high. 



The image enlarges as the distance of the instrument 

 from the screen increases. With a medium objective, a 

 distance of sixteen feet gives a disk of eight feet, &c. 



Exhibitions of this sort appear to the best advantage 



