364 



ERECT IMAGES IN DRAWINGS 



[Cn. X 



vertical. The object is placed upside down in its vertical holder. 

 The mirror reflecting the image upon the vertical drawing surface 

 will give an erect image (fig. 211). 



(B) The objective and the drawing surface horizontal, the 

 object vertical. The artist with his back toward the apparatus : 

 Place the object right side up in the vertical holder. 



(C) Same as above, but with the artist facing the apparatus as 

 with the drawing shelf in fig. 183. Place the object wrong side up 

 in the vertical holder. 



(D) Same, except that a vertical translucent screen is used. 

 Place the object wrong side up in the vertical holder ; do not use a 



FIG. 205. SMALL ARC LAMP WITH CLOCK-WORK FOR FEEDING THE CARBONS. 

 (Cut loaned by Ernst Leitz). 



This arc lamp for the house circuit has a clock-work which moves the carbons 

 continuously. The arc must be started by hand as for a hand-feed lamp, but 

 when once started the lamp will burn continuously provided the carbons burn 

 off as fast as they are fed. If the carbons are too large the clock-work will feed 

 them together faster than they burn away, and if too small the clock-work feeds 

 the carbons too slowly and the lamp will go out. 



The clock-work has a regulating device for speed and the lamp has the usual 

 feed wheel for hand regulation. 



This form of feeding mechanism is equally good for direct and for alternating 

 current as the movement is entirely controlled by the clock-work. Such a 

 lamp is especially useful for drawing and for photography. 



