186 THE NORTHERN MICROSCOPIST. 
ge Se ee 
Vaucheria is very abundant here, upon which may be found /s- 
cularia ornata and Cothurnia imberbis. 1 once found an organism 
very much like the Ophrydium versatile, but living in a single tube 
which I could not identify at the time, and have searched in vain 
for it since. Once I have found Lophopus crystallinus on floating 
timber, and I have but little doubt that it may be found on the 
submerged plants in some of these pits. 

THos. WHITELEGGE. 


ILLUMINATION AND RESOLUTION. 
’ is not unfrequently the case, as we have had sufficient reason 
to know, that when a person first tries to resolve the Amphi- 
pleura pellucida, or some other difficult test-object, with an objective 
that is quite capable of showing the lines, the result is very unsatis- 
factory. Sometimes the lines cannot be seen at all, and we have 
known persons to own such objectives for months, without being 
able to show the lines. There is a “knack” about it, to be sure, 
but it is by no means difficult to acquire. In most cases the fault 
is entirely in the illumination, An adjustable objctive will not re-. 
solve well unless the proper adjustment is made, and the lines on 
a delicate test-object cannot be seen without careful focussing—all 
this is well understood at the beginning. Nevertheless, in most 
cases the greatest difficulty met with by the novice is in the man- 
agement of the light. A few suggestions concerning this matter 
may prove of assistance to some of our readers. 
One may sit at a table and put the elbow on the partly opened 
drawer, and hook the heel of the left foot over the front round of 
the chair, as Prof. J. Edwards Smith has directed in his celebrated 
book. But we can assure the reader that lines ona A. pellucida 
can be reasonably well seen without any such formalities. In truth, 
one of the best resolutions we ever saw was shown by Mr. Herbert 
Spencer, in his shop at Geneva, with light from a cloudy sky, the 
microscope standing on a packing-box, which was also used as a 
seat, if we recollect aright. 
The novice will not succeed as well by daylight as with light 
from a lamp, and the simple, low hand-lamp with a flat wick is the 
best of all. A student-lamp is not good for this work. To get the 
best result, remove all substage accessories and also the mirror. 
Then fasten the Woodward prism, hemispherical lens, or whatever 
attachment may be used in their stead, to the test-plate with gly- 
cerine. It is a good plan to paste a strip of paper on the back of 
the slide for the side of the prism to rest against. This prevents 


