ACCESSORY APPARATUS. 121 



method of mounting was formerly much in vogue, but has been less 

 employed of late, since the Lieberkiihn has fallen into comparative dis- 

 use. The Stage Vice, as made by Mr. Ross for Mr. Slack, was contrived 

 for the purpose of holding small hard bodies, such as Minerals, apt to be 

 jerked out by the angular motion of the blades of the forceps, or very 

 delicate substances that will not bear rough compression. In this appa- 

 ratus the blades meet horizontally, and their movements can be regulated 

 to a nicety with a fine screw. The Stage Vice fits into a plate, as is the 

 case with Beck's disk-holder, Fig. 94. 



119. For the examination of objects which cannot be conveniently 

 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. 94) in regard to the facility it affords for presenting them in 

 every variety of position. 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 project- 

 ing from its under surface into a cylindrical holder; and the holder carry- 

 ing 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 in- 

 cline to one side or to the other, until its plane becomes vertical, by turn- 

 ing the whole movement on the 

 horizontal axis of its cylindrical 

 socket. 1 The supporting plate be- 

 ing perforated by a large aperture, 

 the object may be illuminated by 

 the Lieberkuhn if desired. The 

 disks are inserted into the holder, 

 or are removed from it, by a pair 

 of Forceps constructed for the 

 purpose; and they may be safely Beck's Disk-holder, 



put away, by inserting their stems 



into a plate perforated with holes. Several such plates, with inter- 

 vening 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 facili- 

 tated by it. A less costly substitute, however, which answers sufficiently 

 well for general purposes, is found in the Object-holder of Mr. Morris 

 (Fig. 95), which consists of a supporting plate that carries a ball-and- 

 socket joint in its centre, into the ball of which can be fitted by a taper- 

 ing stem either a holder for small cardboard disks, or a larger holder 

 suitable for carrying an ordinary slide. By the free play of the ball- 

 and-socket joint in different directions, the object may either be made to 

 rotate, or may be so tilted as to be viewed obliquely or almost laterally. 

 This instrument can, of course, be used only by side illumination; and 

 in order to turn it to the best account, the objects to be viewed by it must 

 be mounted on special disks; but it has an advantage over the preceding, 

 in being applicable also to objects mounted in ordinary slides. Ine 

 same purpose is answered, in the Ross Zentmayer Microscopes (59, 

 72), and in the Improved Beck Microscope ( 65), by turning the stage 

 round its horizontal axis, so that an object mounted on a slide may b 



1 A small pair of Forceps adapted to take up minute objects may be fitted into 

 the cylindrical holder, in place of a disk. 



