ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
511 
full set, that is, tlie prism in the path of the optic axis, the image can be 
focused on the grey glass screen C, by means of the adjustable tube. As 
any variation of focus in the Microscope will affect both screens equally, 
all further observations can now be made on the screen C. 
When the shutter is released the prism is carried out of position 
and the plate momentarily exposed as the shutter aperture crosses the 
optic axis, the length of exposure being regulated by the width of the 
shutter aperture, and also by fixing a fan to the pulley. 
Human blood taken directly from the arm to the Microscope has 
been photographed by this apparatus, employing Zeiss apochromatic 
1/8 objective N. A. * 95, projection ocular 3, oxyhydrogen illumination, 
also living specimens of the Kotifera and freshwater animalcula taken 
with lower power objectives. 
Baker’s Photographic Microscope. — This instrument is made o:i 
the lines suggested by Mr. E. Hartley Turner, of Manchester, and con- 
sists of a solid brass base carrying body, stage, and sub-stage. 
The body is 3 in. long by 11- in. diameter, thus ensuring the 
passage of the whole of the rays emergent from even the lowest power 
objectives. It is fitted with universal adapter to carry micro-objectives, 
Fig. 49. 
and its width of tube allows of ordinary short focus photographic lenses 
being used. Mechanical tube-length from 150 mm. to 270 mm. can be 
obtained by the use of draw-tubes. The fine-adjustment is of the 
Campbell differential screw form, and carries only the body, as in the 
large Nelson model Microscope. 
The stage is fitted with sliding bar and removable spring clips, and 
has a clear aperture of 2 in., which can be reduced by diaphragms. 
The instrument can be fitted with mechanical stage if desired. 
The sub-stage is of universal size, and is fitted with rackwork and 
centering screws ; it has also a sliding adjustment, enabling condenseTs, 
differently mounted, to Vbe brought within the limits of the rackwork 
movement. 
All the fittings, are sprung, and provided with adjustable screws to 
compensate for wear. 
1891 2 n 
