510 SUMMARY OK QUERENT RESEARCHES RELATING TO 



possible, and for this purpose the upper surface of the inserted ring has 

 been cut out in such a way that it is in contact with the under surface 

 of the other ring at only three points. The upper ring has in its rim a 

 vertical slit for receiving a fine needle, or bristle, whose end should 

 exactly coincide with the ring centre. A ring, corresponding to the 

 thickness of the diaphragm, has to be soldered on to the ocular so that, 

 when inserted into the tube, the ocular rests on this ring. About 

 1 *5 mm. above this ring in the ocular is a cross-slit extending to about 

 one-fourth of the circumference for receiving the bristle, which should 

 now be sharply defined in the field of view, and should, moreover, be in 

 its centre when the lens rings are concentric. The apparatus requires 

 a special table (85 cm. high, long side 72 cm., short side 51 cm.). 

 The observer sits at one of the short sides (we will suppose at the right 

 of the figure) and at his left hand, 8 cm. from both long and short 

 sides, is a rectangular hole 14 by 11 cm., the 14 cm. corresponding 

 to the short side of table. The table legs are connected by a horizontal 

 cross-board, whose upper surface is 52^ cm. above the floor. The 

 difference of height between this surface and the table-top surface is 

 just sufficient for the object-stage (17^ cm.) and extended draw-tube 

 (170 cm.). In addition, the height of the pantograph and the height 

 of the upper plane of the ocular must be allowed for. The " fixation- 

 point " of the pantograph is seen at the observer's lower left hand. This 

 point is secured by a knob with a pointed top, on which the pantograph 

 hooks. There are, in reality, two of these fixation points : the one 

 shown in use in the figure is 1 cm. from the rectangular hole, and is 

 suitable for strong magnifications ; the other, about 7 cm. away, is for 

 weak magnifications. In the "stay-joint" (diagonally opposite to the 

 object-point, or Microscope) of the pantograph is a rounded knob, which 

 moves to and fro in the rotations about the fixation-point. A little 

 wheel under this knob facilitates the motion and reduces the friction. 

 The wheel, instead of moving on the wooden table-top, moves on a glass 

 plate, thereby securing greater regularity and freedom of motion. The 

 other joints produce a sliding movement of the bars relative to one 

 another. An arrangement is made for artificial illumination, if required. 

 The possible range of magnification was found to be between 2 and 10. 

 This is, of course, quite independent of the ocular magnification, and, 

 therefore, a strong eye-piece is recommended as giving sharper control 

 in the tracing out of the outline. The framework should be made of 

 L-shaped aluminium bars. 



Koristka's Illuminator for Opaque Objects.* — This apparatus is 

 principally intended for the study of metals. It is screwed to the 

 Microscope tube, and contains a total reflexive prism which receives the 

 light from the front and directs it by means of the objective on to the 

 preparation. The prism occupies only half the field, thus leaving the 

 other half free for vision. An iris diaphragm placed in front of the 

 prism serves to regulate the light which it is to receive. By pulling out 

 the arm which carries the prism the latter may be removed from the 



* Koristka's Catalogue, No. 12 (1*.»05) p. 50, fig. 5G. 



