and Laboratory Methods. 



2189 



room we have two lanterns, one at the back of the room with the screen at the 

 front for use with large classes, and the other a small lantern, placed on the 

 speaker's desk and throwing a picture on a side screen. We find that the work 

 is better illustrated where it is possible to use the small lantern, because the 

 instructor can stand before the class and show the slide at the proper time with- 

 out going to the rear of the room and back again, or staying at the rear during 

 the rest of the hour. 



Fig. 2. — Photograph showing a home-made lantern. A shows the body of the lantern. 

 The box is made of sheet iron, and while it is well ventilated, it is light tight, a very essential 

 feature if it is to be used in front of the audience as suggested, a is the slide holder. B is the 

 electric lamp taken out of the box to show its construction. C is the rheostat. The wire is held 

 to the right hand upright in a v-shaped slot in a piece of brass, this enables one to vary the 

 length of the coil and thus change the resistance. 



Another point is in regard to darkening the room. Where rooms have been 

 especially arranged for the use of the lantern in the day time, some method of 

 mechanically raising and lowering the shades is provided. This is certainly 

 most convenient, but is by no means essential. This is especially true where 

 electricity is used. Our own lecture 

 room is in a very old building and 

 has only ordinary window shades. 

 These run behind frames which 

 have been attached to the window 

 casings. The shades are lowered 

 at the beginning of the hour. The 

 room is, however, never completely 

 darkened. Usually the curtains 

 are left up enough to let in light for 

 comfortable note taking. Unless 

 the light shines directly on the 

 screen, the picture is brilliant 

 enough for ordinary purposes. It 

 is a very great convenience to have 

 incandescent lights in the room 

 sufificient for illuminating purposes, 

 with a switch at hand, so that at yig.S. — Diagram showing arrangement of the lantern 

 times when the pictures are not in the lecture room. A is the lantern on the in- 



11 1 • r ^u ™ structor's desk. B is the screen. D is a second 



actually bemg shown the room may j^^^^^^ ^.^^ ^ ^^^^^^, ^^g,^^ l^^^ ^^ be used with 



be well lighted. large classes and throws a picture on the screen E. 



