38 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
bination of the two movements any portion of the plate may be brought 
under the Microscope, and any number of objects arranged thereon may be 
brought into the field in succession. The objects being enclosed in the 
box are secure from injury ; the movement of the Microscope for focal 
adjustment is limited by stops, so that the object cannot be entirely lost 
to view ; the eye-pieces are screwed in so that they cannot be stolen, 
and the instrument is practically safe from everything but malicious 
mischief. The instrument was made originally for exhibiting forami- 
nifera, which were mounted in concave brass discs without stems for 
insertion in the holes of the rotatory stage. For transparent objects the 
Fig. 132. 
stage must be perforated for upward reflection of the light from the 
mirror below. The instrument now in use in the museum was made in 
the year 1890, has been modified in a few details since, and has suc- 
cessfully endured manipulation by thousands of inexpert hands of 
children as well as adults, without injury, and this without attendant 
supervision of any kind. 
In figs. 133, 134, Dr. Flint shows a different form of apparatus in- 
tended for the exhibition of series. An indefinite number of slides are 
attached to an endless band of linen by means of thin brass holders 
which allow the slides to be changed when desired. This linen band 
passes over two rollers mounted upon a light brass frame which occupies 
the place of the stage of an ordinary Microscope. The loops of the 
