Franz Schmidt & Haensch, Berlin S. 



C. Appliances for Objective Demonstration. 



The great practical value of objective demonstration becomes more 

 and more acknowledged and, accordingly, this method of instruction is 

 being adopted by an ever increasing circle of colleges and schools. 

 According to the available means and the source of light, apparatus for 

 various forms of illumination and of varying sizes are in requisition, viz. 

 for lamp, zirconium (coal-gas and oxygen) and electric light. 



I. Appliances for electric light 



of various sizes with double or triple illuminating system and with lenses 

 of 105 to 300 mm diameter according to the size of the object which 

 is to be shown on the screen. The apparatus is fitted with water tank. 

 The contact lamp of von Hefner-Altenek, adjusted for 15, 20 or 

 25 Amperes forms a suitable source of light. 



a. Large Camera lor Elec- 

 tric light, 



own design, made of brass. Per- 

 fectly light-tight casing. The side 

 doors are balanced by counter 

 weights and are made to move 

 upwards. Diameter of the two 

 illuminating lenses 105 mm. The 

 whole lamp can by means of a 

 rack and pinion movement be 

 raised and lowered, and by means 

 of a lateral sliding arrangement 

 the source of illumination can 

 always be brought into the opti- 

 cal axis. 



b. Large Mahogany Camera, 

 lined with asbestos inside; equip- 

 ment otherwise similar to that of a. 



c. Large Camera, 

 own design, of brass fitted with 

 all the above mentioned improve- 

 ments. The carbons are contained in a casing which is accessible by 

 three doors, the lower portion of the lamp being open for manipulation. 

 (Fig. 18.) 



Fig. 18. 



