GEOMETRIC SLIDE APPARATUS 19 



microscope, condensers, and lamp are carried. Fig. 6 

 illustrates a camera made by Messrs. Bausch and Lomb, 

 and Fig. 44 one by Zeiss. Suitable optical benches can be 

 obtained separately, or are supplied with the camera 

 as a complete photomicrographic outfit such as is illus- 

 trated in Figs. 7 and 8. Fig. 7 shows Leitz' large photo- 

 micrographic apparatus with the camera raised into the 

 vertical position. A wheel may be noticed beneath 

 the steel tubes which form the optical bench ; it is used 

 for vertical adjustment of the stand carrying the micro- 

 scope when the camera is used in a horizontal position. 

 A flexible rod is supplied for focussing purposes, carry- 

 ing a little wheel with india-rubber round its circum- 

 ference, and bearing on the side milled heads of the 

 microscope. The bellows of the camera can be drawn 

 away from the back, if it is preferred to focus on white 

 card. 



Mr. Barnard's Geometric Slide Photomicrographic Ap- 

 paratus. Mr. J. E. Barnard has designed a very fine 

 photomicrographic apparatus, in which he has employed 

 the system of the geometric slide in the carriers supporting 

 the camera, microscope, and illuminating system. As 

 made by Baker it is shown at Fig. 8. The camera has an 

 extension of 3 feet, and can be moved vertically on rods 

 fixed to the slides ; a small white screen is supported on 

 one side, and on it the projected image or disc of light 

 may be examined. A carrier for colour screens is attached 

 to the auxiliary condenser a Nelson aplanatic bull's-eye. 

 The lamp shown is a Nernst of one ampere. The con- 

 denser and lamp are both carried on adjustable centring 

 supports. The rails on which the camera runs are hinged 

 to the main casting, and can be raised into a vertical 

 position ; and a strut is provided to hold the camera 

 rigidly over the microscope. The part of the stand 

 carrying the microscope, lamp, and condenser is pivoted 

 so that it can be swung round to enable direct observations 



