72 HOW TO SEE WITH THE MICROSCOPE. 



sive stands, which, with the accompanying accessories, 

 etc., cost $1,600 and upwards, down to the more simple 

 forms, within the reach of all. It is from the latter 

 that we make the following selections : 



BECK'S POPULAR MICROSCOPE, MONOCULAR OR BINOC- 

 ULAR. 



In this stand the arrangement for changing the angle 

 of inclination of the body is new and durable. It has 

 coarse adjustment by rack and pinion, fine adjustment 

 by micrometer screw ; the stage is fitted with improved 

 object-holder and concentric revolving fittings; the 

 mirror slides on the main stem, and has its own semi- 

 circle for universal motions. A diaphragm is provided 

 with perforated revolving disk. The instrument is on 

 the "transverse arm" model, which has been so ex- 

 tensively used by Koss, of London, as well as others. 



The instrument can be furnished with all the usual 

 accessory apparatus as supplied by the makers; a 

 mechanical stage, giving horizontal and vertical motions 

 by screws, is also furnished if desired. 



BECK'S ECONOMIC MICROSCOPE. 



The makers say in their catalogue that " the micro- 

 scope is now such an absolute necessity for the student, 

 to enable him satisfactorily to carry on his investiga- 

 tion, that it is more than ever incumbent on the optician 

 to construct a sound economic instrument adapted to 

 the special requirements of this large and increasing 

 class." 



To this proposition let this little book say, Amen. 



