The Microscope. 



33 



(unlike them) sufficiently firm and manageable for either large 

 or small magnifiers, of low or high powers, and is available for 

 an arm-length of 20 to 25 cm. It consists, as shown in Fig. 1, 



of a rectangular frame which slips over the pillar of a bull's- 

 eye stand, both it and the bull's-eye being best mounted 

 upon the same stand, for the sake of simplifying the apparatus, 

 and because they are often advantageously used in combination. 

 The frame slides smoothly up and down the pillar, being held 

 in any position by an included spring. To an extension of the 

 bottom of the frame is attached a horizontal arm, having first a 

 horizontal pivot joint, and secondly a ball and socket joint, the 

 tension of these being readily adjustable by means of a screw 

 with a large milled head. By bending the joints, the lens may 

 be brought near the pillar for use in connection with the bull's- 

 eye. 



At the end of the arm rises a vertical pivot, upon which 

 can be slipped almost any kind of pocket magnifier, such as a 

 Coddington or achromatic triplet (which on account of its long- 

 working focus and broad, clearly-defined and well-lighted field 

 of view may be considered rather a necessity than a luxury), 



