Diatomacee. 47 
the odour peculiar to obstructions. Such films may also 
occasionally be seen in all ditches with a gentle current, 
where a temporary obstruction impedes circulation ; on water- 
cress beds, and even on water with a rapid current when 
water weeds rise to the surface. 
The nature of such films can, of course, only be seen by the aid 
of the microscope. They are so delicate, so gossamer-like, that 
they cannot be handled without altogether altering the form. 
The substance breaks up easily, and this no doubt was the origin 
of the term diatoms, which in times past were called brittleworts 
or brittleweeds. The film may be collected in a bottle in the 
usual way, but sometimes one will be observed when the neces- 
sary apparatus is athome. The best plan then is to walk in, if 
the water be not too deep, carry it home on the end of the 
stick or umbrella, and allow a very small quantity of water to 
wash it from the stick into a small glass. It will in a short 
time be found on the surface ready for examination, and will 
be found to consist of diatoms of various sizes, conferve and 
infusoria, the last revelling in the rich banquet which nature 
has provided them. I have mounted roughly a slide or two at 
numbers 1 and 2. They are not very beautiful, but they are 
very interesting. You will find, growing together, young 
diatoms and conferve—the diatoms, in many cases, attached 
to a confer. 
Passing now from what presents itself on the surface 
and from what is sometimes unpleasant — from surface 
growth to undergrowth—you cannot fail to observe two things, 
the extraordinary beauty of the subaqueous scenery, and the 
apparently repulsive appearance which a portion of it presents 
when removed from the water. This beautiful miniature 
scenery is, in a great measure, due to the presence of the 
diatom. I may indeed venture to say that, but for the diatom, 
much that excites admiration would disappear, and nothing be 
left but bare stone. Remove any of these undergrowths—the 
velvety cushion from the stone, or the long lines of freely 
flowing ‘“silkweed of the country” from the water, how 
different they appear! Many a person has turned from them 
in disgust, but this must not be the case with the student. 
He must take them home, put them into a glass, add water, 
stir them, allow the heavier particles to subside, take a small 
quantity with a tube, place it on a slide, and then he will find 
that he has robbed the water of some of its treasures. In 
some of these experiments some diatoms will be found quite 
- free; others united end to end, so as to form a filament; 
while others will be seen firmly attached to conferve. Speci- 
mens of various kinds may be seen at 3, 4, 5, in their 
natural state. At 6, 7,8, you have the part coveted by the 
