STAGE-FORCEPS — GLASS STAGE-PLATE. 147 



rated from the other; and the blades close again, so as to retain 

 the object when the pressure is withdrawn. By sliding the wire 

 stem which bears the forceps through its socket, and by moving 

 that socket vertically upon its joint, and the joint hoi'izontally 



Fig. 47. 



Slage-Forceps. 



upon the pin, the object may be brought into the field precisely 

 in the position required; and it may be turned round and 

 round, so that all sides of it may be_ examined by simply giving 

 a twisting movement to the wire stem. The other extremity of 

 the stem often bears a small brass box filled with cork, and per- 

 forated with holes in its side ; this affords a secure hold to com- 

 mon pins, to which disks of card, &c., maybe attached, whereon 

 objects are mounted for being viewed with the Lieberkiihn. 

 This method of mounting was formerly much in vogue, but has 

 been less employed of late, since the Lieberkiihn has fallen into 

 comparative disuse. 



67. Glass Stage-Plate. — Every Microscope should be furnished 

 with a piece of plate-glass, about 4 in. by IJ in., to one margin 

 of which a narrow strip of glass is cemented, so as to form a 

 ledge. This is extremely useful, both for laying objects upon 

 (the ledge preventing them from sliding down when the micro- 

 scope is inclined), and for preserving the stage fi'om injury by 

 spilling of sea-water or other saline or corrosive liquids, when 

 such are in use. Such a plate not only serves for the examina- 

 tion of transparent, but also of opaque objects ; the dark back- 

 ground being furnished by the diaphragm-plate (§ 55), and the 

 condensing-lens being so placed as to throw a side-light upon 

 them. A small addition may be conveniently made to the glass 

 stage-plate, which adapts it for use as a Crrowing-Slide. A circu- 

 lar aperture, of about the diameter of a test-tube, is made near 

 one end of the plate (the length of which, for this purpose, had 

 better be not less than 5 inches), and in this is to be fitted a 

 little cup, formed of the end of a test-tube, about three-quarters 

 of an inch deep, in such a manner that its rim shall project a little 

 above the surface of the plate. The cup may be closed by an 

 ordinary cork, or (to avoid the danger of splitting it) by a disk 

 of glass cemented to a ring of cork which shall embrace the ex- 

 terior of the tube ; but a small aperture must be left, by grind- 

 ing a notch in the rim of the cup, sufficient to admit the passage 

 of two or three threads of lamp-cotton. The manner in which the 

 " growing-slide" is used, is this : — Supposing we wish to follow 

 the changes undergone by some minute Alga or Infusorium, which 



