MIDLAND NATURALIST. , AS 
and examining material in the field. This device is simply a 
modified demonstration microscope used in class examination of 
objects. The handle usually seen attached to the apparatus in the 
optical catalogues, is left off and the base is cut down to a narrow 
circular outline, so as to fit easily into the collector’s pocket. A 
piece of Gooch tubing is stretched over the brass fittings of the 
instrument, to protect it from the corrosive action of the water and 
dirt. The ocular may be protected by a rubber cap and the ob- 
jective is always kept from injury by the thick slide securely held 
by two clamps. The lenses most convenient are found to be either 
a two-thirds objective, with a wide aperture, and one inch or one- 
half inch ocular, or a one-half inch objective with a one inch ocular. 
Any higher power of objective combination than those indicated, 
was found difficult to focus, as there is no micrometer adjustment, 
and if one were present would be very inconvenient to work. 
one-fourth inch objective was used but was discarded owing to the 
fact that it could not be rapidly brought to focus. 
In making an examination, a small amount of the material is 
put on the outside of the slide, then held up to the light and by 
turning the tube may be focused. If a drop of water is examined 
for unicellular plants, the microscope may be held downwards to the 
reflection of the light of the sky from the water. A cover-glass is 
very desirable, though it is never really necessary except with uni- 
c?llular forms. 
Experience has shown that it is hardly ever necessary to use a 
combination higher than a two-thirds-inch objective, and a one-inch 
ocular. Such difficult materialas conjugating desmids 15 to 15 microns 
in diameter were clearly and conclusively demonstrated with the com- 
aperture of the objective the better results will be attained, owing 
to the fact that the wide aperture takes in a broader field. The 
usefulness of the instrument, as a demonstration microscope is not 
impaired in the least, and the handle can be replaced in a few 
moments. The type for field use is always kept nearly in focus by 
the Gooch tubing which is doubled on itself near the eye-piece to 
obviate wear on the milled parts of the microscope. Its simple 
construction makes it easy for students to use it with little danger 
or injury and all working parts are so thoroughly concealed that it 
is practically impossible for dust and dirt to penetrate. a 
Laboratory of Botanical por 
i University of Notre Dame 
