122 



MECHANICAL ARRANGEMENT OF THE MICROSCOPE. 



II. 



THE STANDS OF MODEKN OPTICIANS. 



WE now proceed to describe a type-model stand that has met with 



much favour among the leading firms of Continental opticians. 

 Dr. E. Hartnack, of Potsdam, and A. Prazmowski, of Paris- 



(formerly the firm of Hartnack & Prazmowski, successors to 



G. Oberhseuser) : The large older 

 horse-shoe stand of Oberhaeuser 

 (Fig. 51), which these opticians 

 have retained without essential 

 alterations, and which many other 

 opticians have adopted with more 

 or less modifications, has already 

 been referred to as an excellent 

 type-model. It deserves this ap- 

 pellation, because it combines, as 

 no other does, the advantages of 

 the greatest efficiency with sim- 

 plicity of construction. The 

 coarse adjustment is effected by 

 sliding the tube in the socket, 

 and the fine adjustment by a 

 micrometer-screw, which raises 

 and lowers the socket. The stage 

 revolves, and carries the optical 

 body round with it ; it is pro- 

 vided on its under surface with 

 grooves in which the substage 

 slides carrying the condenser or 

 diaphragms; the mirror is movable 

 laterally and vertically, one side 

 being plane, the other concave. 



Kecently these opticians have 

 somewhat altered the construc- 

 tion of this stand, by supplying, 



amongst other things, rackwork for the coarse adjustment. 



[We have thought it preferable to omit any translation of the 



other parts of this chapter, which are descriptive of stands, as the 



FIG. 51. 



