5 

 is clamped to it^ pillar by three set-screws, and by means of this 

 simple arrangement the microscope can be fixed high or low 

 to suit different operators and different classes of work. When, 

 for instance, micro-photographs are being taken, it is most con- 

 venient to drop the sleeve to its lowest limit, so that the micro- 

 scope will rest on a base about fifteen inches above the floor. 

 For most photo-micrographic work this will enable the operator 

 to bring the focussing plate of the camera (19 Fig. i) low enough 

 to render it unnecessary for the pperator tO' have any special step- 

 ladder to assist him in obtaining an accurate focus. On the other 

 hand, w'hen it is necessary to place the microscope high and the 

 camera lucida table low, one can obtain a distance as great as two 

 and one-half feet between the level of the eye-piece of the micro- 

 scope and the drawing table. This, together with the peculiar 

 camera lucida, which will be described later on, enables one to 

 make his original sketches of such a size as to allow for that 

 liberal reduction in the subsequent photographic process which 

 gives the best results for book illustrations. The sleeve which 

 carries the microscope also carries a wooden front as wide as 

 the microscope window and about two feet deep, in other words 

 about three feet by two feet. This screen, which of course slides 

 up and down with the microscope and its sleeve, carries two 

 apertures. One of these apertures is in front of the microscope 

 mirror and is designed to allow the light from the special out- 

 door illuminating screen to strike the mirror and pass through 

 the microscope. The second aperture is of much larger size 

 and is glazed with ground glass and is opened or closed as de- 

 sired by means of a 'hanging slide worked by foot-power. The 

 object of this second opening is to secure a correct illumination 

 on the drawing board when the camera lucida is in use. See Fig. 

 I. 



We will next pass to a description of the microscope win- 

 dow. This faces the sun, and preferably faces precisely soutlk 

 It is so fitted with light-proof roller blinds that the light 

 may be entirely shut off or may be allowed full access. The 

 roller blinds slide in lateral grooves ten inches deep. The depth 

 of these grooves must be sufficient to prevent the blinds belly- 

 ing through the action of the wind. It is found when a window 

 is tightly closed with flexible blinds as is the case in this special 

 microscope window, that the pressure of the wind is sufficient 

 to cause considerable inconvenience unless the edges of these 

 roller blinds are held in deep grooves. Should it be necessary 

 to make a further provision against tbe bellying of the blinds 

 they may be stiffened from place to place with one-sixteenth- 

 inch wooden laths; or wires may be strung across the window. 

 The blinds may be of any opaque material, but if they are very 



