90 PRACTICAL MICROSCOPY. 



no damage is done, on account of the object receding as 

 soon as contact is made, the springs shown in the figure 

 making that motion possible. The object is placed on the 

 two short arms C C, and is held in its place by the spring, 

 which is placed above and between them. In order to 

 make safety doubly sure Mr. Stephenson has devised a 

 second piece of apparatus to act with the former; it is 

 shown in Fig. 79, and consists of a square rod of brass which 



FIG. 80. 



must be adjusted to suit the various objectives used ; it is 

 held in its place by a pin passing through it, attached 

 to a screw at the outer side of the socket in which the rod 

 slides. This instrument is placed (in the Ross model) 

 beneath the bar which carries the microscope body, and, 

 when properly adjusted, allows the objective to touch 

 the object upon the stage, but arrests all further progress, 

 no matter with what degree of force the coarse adjustment 



