216 BENJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE. 



the same size and power. The lanterns, A, B, should be 

 placed side by side on two slabs of wood, C, C ; these pieces 

 of wood turn upon a screw, and are firmly fixed in their 

 places by the thumb screw behind the lantern. The slabs, 

 C, C, are screwed upon a larger piece of wood, E, about 

 two feet square, so that they may be inclined to such an 

 angle, that the circle of light from the two lanterns, may 

 exactly coincide upon the screen, as though the light was 

 proceeding from one instrument. It is also of much conse- 

 quence that the paintings are placed in the centre of the 

 lenses, this is easily accomplished by means of the mahogany 

 guide, fig. 3, which is shown in its position at H, fig. 1. 



The lamps having been made to burn brilliantly and put 

 into their places, incline each instrument until the light falls 

 exactly upon the same spot upon the screen ; then give the 

 thumb screw a turn, which will retain the lanterns at the 

 angle required. It will be seen that the lanterns are kept 

 down upon the slabs by means of the handles, D D. A 

 painting is now to be introduced, and the focus adjusted by 

 means of the tubes, a 6; the crescent formed shade, F, is 

 then to be drawn pretty close to the pipes, and secured by 

 the thumb screw, I, fig. 2, the object being to cover and 

 uncover each aperture alternately. It will be evident that 

 as the shade is caused to make its half revolution, by turn- 

 ing the handle, it follows that the moment the shade begins 

 to cover A, a corresponding part is exposed of the painting 

 in B, and the more slowly this shade is made to revolve, 

 the more gradual will be the change ; the picture in A im- 

 perceptibly melting into the one in B. There is a pin in the 

 rod which turns the shade, F, so that it can only be made 

 to move the half revolution. To make a change, remove 

 the painting in A, and replace it by another, then gently 

 reversing the operation. 



The guide, fig. 3, will be found of essential service ; it is 

 made to fit tightly the opening of the lantern which receives 

 the sliders ; this guide is exactly the length of the sliders, 

 and is so fitted, that when the sliders are pressed down 

 upon it, and the ends of the sliders correspond with the ends 

 of the guide, the exhibitor is sure that his painting is in its 

 central position ; it is of course supposed that each picture 

 is in a separate slider, and that the paintings are in the 

 centres of the sliders. 



