1 64 



THE MICROSCOPE. 



centric rings turned about the centre of the latter, — and held in 

 position by the usual spring clips, — the guide plate is moved up 

 until the lower left hand corner of the slide rests securely in the 

 angle formed by the upper edge of the guide and the stop at its 

 left; when the milled head is screwed up tight and the centering 

 arrangement is ready to do its allotted work. It follows that any 

 rectangular slide 3x1 inches, slipped under the spring clips and 

 into the angle of the guide, must have its centre exactly over that of 



TURN TABLE. 



the table, and a ring of cement once run upon it when so placed, 

 can be followed by as many more as are desirable, by simply replac- 

 ing the slide in the same angle, without any trouble in adjusting. 

 Since, however, very few slides are absolutely rectangular or have 

 exactly parallel edges, it will be found convenient in practice, to 



WKiriNCr DIAMOND. 



place a mark upon the left hand end of each before running the 

 first layer of cement thereon, after which it may be 

 replaced as often as desired, without loss of time. A writing 

 diamond is the most convenient tool for doing this with, but 



