154 



SUMMARY OF CURRENT RESEARCHES RELATING TO 



three small bearing-plates c c c. The circle-segment which the middle 

 point h describes when the apparatus is moved must accurately intersect 

 the middle of the field of view. The movement of the ring A is limited on 

 the left side by the clamp D, which is movable, and can be fixed in any 

 desired position by a screw. On the right the motion is confined by the 

 adjusting-screw E attached to the stage F. The disc B, perforated by 

 the quadrangular opening d d d d, carries the frame C which is fixed to B 

 by the binding-screws e e e e. To the left of the frame is the handle /, 

 havinc a slight tilt upwards. In the long sides of the frame C are grooves 

 in which the screws e work ; if the latter are drawn out, the frame can be 

 moved in the direction of its length. The frame C carries a glass plate, 

 two springs g g, and a narrow plate h ; these last three lie upon the glass 

 so as to leave spaces for the insertion of cover-glasses a and y of 10 and 

 6 mm. diameter, the former carrying the specimens from which are selected 

 those to be arranged on the latter. 



It follows, therefore, from the construction of the apparatus, that if the 

 centre of the cover-glass y coincide with the central point h, the central 

 point of the fielii of vision will revolve round its own axis when B is turned, 

 provided that the clamp D is so adjusted that the outer frame A touches it. 

 Similarly, when the frame is properly adjusted to E, the centre of a will 

 remain in the field of view. 



The chief advantage of this instrument consists in its automatic pre- 

 cision, the hair used for arranging being always within the field of view and 

 under the control of the preparer. 



Hildebrand's Slide-carrier.* — In Dr. H. E. Hildebrand's contrivance 

 (figs. 22-24) the stage is fitted with a circular frame E, in which is inclosed 



Fm. 23. 



X V 



a glass plate P with a central aperture. The slide-carrier proper is a metal 

 plate F, with a circular opening in the middle. This plate moves over 



* Zeitsclir. f. Wiss. Mikr., iii. (188G) pp. 38G-9 (3 figs ). 



