ACCESSORY INSTRUMENTS. 129 



pair of blades, fitting closely together by their own elasticity, 

 but which, for the reception of any object, may be separated 



Fig. 80. 



by pressing the two projecting studs ; to the opposite end of 

 the wire is adapted a small brass cup, filled with cork, into 

 which, pins passed through discs of cork, cardboard, or other 

 material having objects mounted on them, may be stuck ; or, 

 if preferred, instead of the cork, a pair of blades, fitting accu- 

 rately together, may be employed, with small notches in each, 

 to receive the pins. With aU the old microscopes, one end of 

 the wire carrying the forceps was made pointed, and to it was 

 adapted a small cylindrical piece of ivory, having one of its 

 ends white and the other black, on these surfaces the objects 

 for examination were laid. Mr. Ross and Mr. Smith some- 

 times supply a pair of three-pronged forceps ; the prongs are 

 made of steel wire, curved and pointed at one end, and by 

 means of a sliding ring, capable of being opened or closed. An 

 instrument of this kind was in use as long ago as 1787, and is 

 - figured in the work of the younger Adams, published in that 

 year. The method of using these different forms of forceps is 

 extremely simple : the object-plate of the stage of the micro- 

 scope has one or more holes, into which the pin of the 

 forceps may fit; on this pin they may be turned in a hori- 

 zontal direction, and by the joint above the pin they may also 

 be inclined at any angle; when once adjusted, the stage 

 movements will suflSce to bring all the parts of the object 

 which they hold into the field of view in succession. With 

 some of the foreign microscopes are supplied other forms of 

 forceps, constructed after the plan of our spring pliers or 

 scissors; one of these, with flat lips for holding objects, se- 

 cured to the object- plate of the stage, and another, either held 



