128 APPENDAGES TO THE MICROSCOPE. 



by gum, or to which disks of card, &c, may be attached, 

 whereon objects are mounted for being viewed with the Lieberkuhn 

 (§ 92). This method of mounting was formerly much in vogue, 

 but has been less employed of late, since the Lieberkuhn has fallen 

 into comparative disuse. 



95. For the examination of Objects which cannot be con- 



Fig. 76. 



Beck's Disk-Holder. 



veniently held in the Stage-forceps, but which can be temporarily 

 or permanently attached to Disks, no means is comparable to 

 the Disk- Holder of Mr. R. Beck (Fig. 76) in regard to the 

 facility it affords for presenting them in every variety of posi- 

 tion. The Object being attached by gum (having a small quantity 

 of glycerine mixed with it), or by gold-size, to the surface of a 

 small blackened metallic Disk, this is fitted by a short stem pro- 

 jecting from its under surface into a cylindrical holder ; and the 

 holder, carrying the disk, can be made to rotate around a vertical 

 axis by turning the milled head on the right, which acts on it by 

 means of a small chain that works through the horizontal tubular 

 stem ; whilst it can be made to incline to one side or to the other, 

 until its plane becomes vertical, by turning the whole movement 

 on the horizontal axis of its cylindrical socket.* The supporting 

 plate being perforated by a large aperture, the object may be illu- 

 minated by the Lieberkuhn if desired. The Disks are inserted 

 into the Holder, or are removed from it, by a pair of Forceps con- 

 structed for the purpose ; and they may be safely put away by 

 inserting their stems into a plate perforated with holes. Several 

 such plates, with intervening guards to prevent them from coming 

 into too close apposition, may be packed into a small box. To the 

 value of this little piece of apparatus the Author can bear the 

 strongest testimony from his own experience, having found his 

 study of the Foraminifera greatly facilitated by it. — A less costly 

 substitute, however, which answers sufficiently well for general 

 purposes, is found in the Object- Holder of Mr. Morris (Fig. 77), 

 which consists of a supporting plate that carries a ball-and-socket 



* A small pair of Forceps adapted to take up minute objects may be 

 fitted into the cylindrical Holder, in place of a disk, as proposed by Capt. 

 Hutton (See " Quart. Journ. of Microsc. Science," N.S. Vol. vi. p. 61). 



