398 EXPERIMENTS WITH THE FLAME -MANOMETER. 



a line fa be drawn from/, perpendicular upon 1 1, and 

 produced so that its production is equal to /a, the place 

 is found where the image is formed; in the figure this 

 place is marked by the number 1. The image will, 

 however, appear only at 1 as long as the mirror has the 

 position II; when this side of the mirror arrives at 

 the position II II, the image of the flame is found, by 

 a similar construction, to be at the place marked by 

 number 2; when the side II is at III III, the image 

 of the flame is at 3, and so on. While the side of the 



FIG. 236. 



mirror turns from the position 1 1 to the position V Y, 

 the image moves successively from 1 to 2, 3, 4 and 5. 

 If the flame burns steadily, it will appear in the mirror 

 as a narrow band between 1 and 5 ; but if it consists of 

 a series of single rapidly succeeding ignitions, a series 

 of single images of the flames will appear side by side 

 in the mirror, as in fig. 236, A. The distance of the 

 individual images from one another depends upon the 

 velocity with which the box rotates and upon the pitch 



