20 MAGIC LANTERN WITH DIRECT CURRENT [Cn. I 



If the slides are not marked, and the correct position must be 

 determined for each individual slide during the exhibition, even 

 the most expert operator is liable to make mistakes, especially 

 when the slides are shown rapidly. 



24. Inspection of the room and lantern by the lecturer. It 



is highly desirable that the lecturer make himself acquainted with 

 the room in which he is to speak, and inspect the lantern himself 

 before the lecture hour. If the operator is with him it gives 

 opportunity to establish pleasant relations, and to stimulate the 

 operator to make the best exhibition possible. It also gives oppor- 

 tunity and time to make any slight changes necessary to insure a 

 good exhibition. Foresight is always more satisfactory in its 

 results than hindsight. 



25. Directions for the operator. The lecturer should in- 

 struct the operator how he wishes the slides shown. There must 

 be some signal for changing the slides. Preferably the signaling 

 device is some form of electric signal on the operator's table, then 

 he can see or hear it, but the audience will not be distracted by it, 

 as when the lecturer has to speak to the operator, or hammer on 

 the floor with the pointer, etc. (For signaling devices see the list 

 of apparatus in the appendix). 



The lecturer should direct the operator to light the lantern 

 before the room lights are extinguished, and give ample warning. 

 The operator should also be told to leave the lantern burning 

 until the room lights are turned on. 



SUGGESTIONS TO THE OPERATOR 



26. Testing the lantern. Before every exhibition or demon- 

 stration the operator should make sure that the lantern is in good 

 working order. This is only fair to the speaker who depends upon 

 his illustrations which he has taken so much trouble and expense to 

 prepare. If the slides are not well shown it injures the effect of the 

 lecture or demonstration and makes it difficult or impossible for 

 the speaker to make clear the subject he is treating. It also dis- 

 quiets the audience; and should make the operator uncomfortable. 



