SMITH AND BECK S STUDENT S MICROSCOPE. 



65 



Fig. 35. 



graduated to inches and tenths : the advantages of this arrange- 

 ment will be explained hereafter (§ 63). The ' fine ' adjustment 

 is effected by means of a milled-head, situated just behind the base 

 of the stem that bears the ' limb ; ' this acts on a screw, the turning 

 of which (by a contrivance that need not be described in detail) 

 depresses the stem with the limb and body attached to it, so as to 

 bring the objective nearer to the object; whilst if the pressure of 

 the screw be with- 

 drawn by turning 

 the milled-head 

 in the opposite 

 direction, the tu- 

 bular stem (with 

 the limb and body) 

 is carried upwards 

 by a spiral spring 

 in its interior, 

 thus increasing the 

 distance of the 

 objective from the 

 object. This ad- 

 justment is re- 

 markable for its 

 sensitiveness, and 

 for its freedom 

 from any displa- 

 cing action upon 

 the image. The 

 only other pecu- 

 liarity that need 

 be noticed in this 

 instrument, is the 

 mode in which the 

 object is borne 

 upon the Stage ; 

 for instead of rest- 

 ing against a ledge, 

 it lies upon a kind 

 of fork, which 

 slides in grooves 

 ploughed out of 

 the stage, and 

 which moves with 

 such facility, that 

 the pressure of a 

 single finger upon 

 one of the upright 



pins at the back Smith and Beck's Student's Microscope. 



F 



