34 
THE YOUNG SCIENTIST. 
the cut, so that when the cutting edge of 
the tool has entered the wood to the requis- 
ite depth, the flat face of the tool will pre- 
vent the edge from entering any deeper. 
In cutting down a radial face the acute 
corner of the tool leads the cut, whereas in 
plain cylindrical work the obtuse is better 
to lead. 
For cutting down the ends, for getting 
into small square corners, and especially for 
small work, the skew chisel is more handy 
than the ordinary chisel, and leaves less 
work for the sandpaper to do. Beginners 
will do well to practice upon black walnut, 
or any wood that is not too soft, roughly 
preparing it with an axe to something near 
a round shape. 
What is a Diatom ? 
IITE. CHAKLES STODDER answers 
this question in the Science Observer: 
I take my instrument from its case, put 
on a 1-6 or a 1-10 objective, and on the 
stage an Aulacodiscus Oregonus or a Coscino- 
discus oculis iridis, anjl tell them to look. 
Then follow the exclamations: how beauti- 
ful! how mathematically regular! what ex- 
quisite lacework ! Then an effort to see the 
object on the slide without the microscope. 
I take the slide off, hold it to the light, and 
there is nothing visible. Then follows the 
question, What is it? I give, perhaps, the 
specific name, but that conveys no idea; 
then I say it is a diatom. But to most 
people that also is without meaning (the 
word not being in Worcester), and the 
question follows, What is a diatom? That 
question I propose to answer here very 
briefly and imperfectly, for a full reply 
would require volumes, some of the most 
costly works published being devoted to 
the diatoms, Ehrenberg's '* Micro-Geo- 
logy," Schmidt's "Atlas," (now being pub- 
lished), to be followed by Prof. Ham- 
ilton L. Smith's great work, the work of 
many years. 
Botanists divide all vegetation into two 
great groups, flowering and flowerless. 
Diatoms are plants, belonging to the flower- 
less class, or algae. They are unicellular, 
i. e.y the whole plant is one single cell; they 
are all microscopic, only a few of the thou- 
sands of named species are visible to the 
naked eye, and then only as mere specks, 
but the eye must be armed with the micro- 
scope to make out the detail of the struc- 
ture of the largest, while for the study of 
the details of the smallest forms the very 
highest quality of instrument must be used,^ 
together with a magnifying power — which 
is an entirely different thing from quality — 
that was scarcely attempted twenty-five 
years ago. Probably no scientific study has 
so much promoted the great improvement 
in microscopic lenses that has been made in 
England and America during the last thirty 
years as the study of these almost invisible 
organisms. Every advance in the know- 
ledge of their structure or growth has pro- 
duced the inquiry. Is this all, or is there 
something yet unseen? This could be an- 
swered only by producing lenses of better 
quality. The diatom cell is filled with the 
living matter of plants, endochrome and 
protoplasm, enclosed in a box of silica, 
secreted and deposited by the cell contents; 
this siliceous shell is its characteristic dis- 
tinction from all other vegetable growths. 
The shells are beautifully sculptured with 
dots, lines, hexagons, and blank spaces, 
making them, as seen in the microscope, 
among the most beautiful objects of nature, 
always exciting an interest in those who see 
them for the first time, and in those who 
have made them the study of years. 
They are found living abundantly in both 
fresh and sea water. Their dead siliceous 
shells are found under almost every peat 
bog; they are found fossilized in the Mio- 
cene Tertiary strata, in Maryland and Vir- 
ginia, and in foreign countries; and when 
free from sand are used for tripoli, or pol- 
ishing powder. The so-called electro-sili- 
con from Nevada, is pure diatom shells. 
This article will be enough to answer the 
question, "What are diatoms?" but to 
learn more, the inquirer must first catch 
his microscope, and then study them in 
earnest. 
