MICROSCOPY. 637 
SEPARATING Dratoms.— In cleaning diatoms, and in preparing 
other microscopic specimens, it is often necessary to decant part 
of the fluid in a vessel without disturbing the remainder, in order 
to separate those objects or particles which are heavy and settle 
promptly from those which are lighter and remain longer diffused 
through the liquid. When no great nicety is required, the upper 
portion of the liquid may simply be 
poured carefully off from the lower; as 
in washing sediments, where all but the 
‘ heavier part is to be thrown away. 
much better separation is accomplished 
by a syphon, either the upper or the low- / 
d er portion, preferably the latter, being 
quietly drawn off by this means. This 
apparatus is so simple as to be easily 
made and managed, and easily cleaned C= 
for subsequent use. Of the more com- 
plicated contrivances for this use, one 
of the best is Benning’s (See Nave’s : 
: Collector’s Hand Book of Alge, etc., = 
= London, 1869, p. 26), which consists pre ge 
of a tall jar with a series of stop-cocks or taps at various heights, 
the water containing the objects being conducted by a funnel to 
the bottom of the jar, and the objects escaping with the water 
from the various taps according to the readiness with which they 
settle through the water. Another plan, a modification by John 
H. Martin of a previously used apparatus (see Martins Manual 
of Microscopic Mounting, London, 1872, p. 24), consists of a 
closed cylinder with several tubes leading through the top, the 
lower ends of these tubes opening inside of the cylinder at dif- 
ferent heights, and the fluid being forced out through them by the 
Pressure of a column of water carried in a flexible rubber tube. 
The disadvantages of these contrivances are their complexity, diffi- 
culty of cleaning, and danger of imperfect cleaning. A simpler 
arrangement is to use a tube drawn out to a funnel-shape at the 
bottom, and closed below by a spring-tap consisting of a rubber 
tube pressed together by a wire spring as represented in the cut. 
apparatus, described in the “ Collectors Hand Book” (p. 
2) and elsewhere, is easily worked and cleaned, and eminently 
ry. Though much used abroad, it has scarcely been 
adopted i in this country. 
Fig. 153. 
SSS E o a 
