32 



R. Jung, Heidelberg. 



40. Thoma's drawing 

 apparatus, for low 

 magnifications and 

 reductions (1 to 10 

 diameters) , with 

 large field, drawing 

 paper on horizontal 

 plane (Fig. 18). 



Fig. 17. 



Fig. 18. Fig. 19. 



41. Illuminating lens on stand, 10 cm diameter, with fitting for 

 placing coloured glasses before the lens. 



42. Rotating double acting air pump for laboratory purposes, in- 

 jecting, air compressing, transmission of gases etc. Quick working 

 up to 125 cm of the mercury pressure gauge. (Fig. 19.) 



