The Helena independent. [volume] (Helena, Mont.) 1875-1943, 1894-03-02
A Remarkable Mill That Is opsr-
atsd by the U. S. Geologi-
cal Survey.
Interesting Discoveries Arc Made
In This Petrifisd Lumber
Mill
Aids In MAILING Up Geological History
The Band Saw and How II -
Worked.

petrined lumber mill operated by the
geological survey. II isa an institution that
has not many visitors, its location down
in the basement Of the survey building ON
j street being rather out Of the track of
the regulation sightseer, but there the sur
vey lapidaries grind thin sections of rock
and minerals of all sorts for microscopic
examination, and there Is a band saw, the
Invention Of the survey, that will cut any
thing from hot butter 20 "A quartz crystal.
Lately the scientists have been saving
mp a lot Of vegetable pctrifactions from
Idaho. They can carve up anything In the
shape of petrified logs that they can get
in front OF their saving machine. Even
the ossiiied man Of the dime museum
would not be safe ,cm, and indeed,
lately, they were called on TO cut mp pet
rifed woman, one that was on exhibition
in Washington. After they had bored into
one Of the damsel's lower limbs little
way they struck a gas pipe. The petrifed
lady was made out Of portland cement,
and the scientists gave her up as n hard
case, which, in fact, she was.
But the most interesting case that has
come 20 the petrified lumber mill was
known as "A cycad "A sort OF vegeta bic par
asite which fourished in the prehistoric
forests of the country some millions Of
years ago, before the woolly elephants and
saber toothed tigers had made their APP
pearance in the businesses OF the Rocky
mountains, and even further back than
local traditions are carried in Alexandria.
The cycads were practically an unknown
quantity. The lot sent it was in fact, the
greatest collection that had ever been gath
cred, some small specimens having been
secured by the British museum, but moth
e, a
one that Is now at the National museum.
One of the small ones, weighing 35 or 40
pounds, WAS sent up 90 the survey 70 have
some sections made for microscopic exam
ination. IL looked very much like a cocoa
nut with the husk on and was cut up
almost as easily as though IL had never
been petrfed.
The band saw used in the work Is moth
ing more than an endless steel wire be
tween an eighth and a sixteenth Of an inch
thick, running at very high rate Of speed
over two good sized fiywheels. Water
and emery are fed on the wire as IL runs,
and the saw comes as near being an ire
sistible force as anything known in the
cutting line. Since the invention Of the
wire saw in the survey Il has been copied
by a number Of Laboratories and lapidary
esta Adjustments all over the country.
Besides the saw there are a number of
grinding machines, smooth iron plates re-
volving like grindstones fat side up and
flooded with water and emery. On these
plates sections of stone for microscOpical
examination can be ground a thousandth
of an inch or less in thickness, so as TO be
perfectly translucent under strong light.
These sections are usually not larger than
10 cent piece, but in examining the cy
cad a section was wanted big enough to
show the plan Of cell growth, and a slab
was cut almost as large as a mans hand.
This, like all Of the stone specimens, after
having one side ground perfectly fat, was
transferred TO glass plate, 10 which It
was fastened with Canada balsam. 1t
is a very beautiful specimen, showing in
prismatic colors the lines of cell partitions
and annular layers like the rings of n tree
trunk.
The lapidary establishment is one Of
the most essential aids that the geological
survey has in working up the geology Of
the country. Many Of the rocks that are
met within the field cannot be distinguish
ed from each other, except by laboratory
examination, and as the nature of the
rocks filling the different sections of the
country has o be ascertained In working
up its geological history the specimens,
carefully labeled, have 10 be sent back to
the department in Washington for study
and classification
Three methods are used in the identifi-
cation of the close grained metamorphic
rocks that cannot be recognized on casual
examination-by measuring the number
and angles Of the crystals, by chemical
analysis to get at the chemical constitu-
ents Of the rock, aud by microscopic ex-
animation, when, in the thin sections, the
crystalline structure can be seen and the
chemical constituents recognized by the
aid Of polarized light Some of the thin
stone sections mounted on glass slides are
very beautiful in coloring and crystalline
arrangement, and others are simply curl
Gus One Of the most remarkable is one
of the rare minerals, dumoritite, which
has lately been discovered in Arizona, and
is what is known as pleochroic.
When viewed under the microscope, IL
seems 10 be made up Of detached crystals
of deep blue. When, however, the slide is
turned around at different angle, some
Of the blue crystals disappear and others
spring into view
One Of the minerals. Of which there are
several deposits In this country. which are
shown in the geological survey : collection
OF slides, Is peridotite. This gains interest
from the fact that 10 g. the associate Of
the diamond IN all OF the great African
fields. Its finding by Professor Lewis Of
Philadelphia In Kentucky some years ago
caused great excitement, and there was
some warm prospecting for diamonds, but
none was ever found. its connection
with the African diamonds came from the
fact that when the peridotite had come TO
the surface In a molten condition Il bad
been forced through the clefts or faults in
some very rich carbouiferous slate fields.
The hot rock had orystallized the carbon
IT the slate measures into diamonds, which
are found scattered along few yards on
each side Of the contact. What the dia-
mond prospectors are looking for I'm this
country Il n combination OF peridotre and
carbonferous states. Whether they will
find IL or not Is question.
One Of the many searchers after Rrtih-
cial diamonds lately made an important
discovery that Is being utilized by the sur
vey aud by many manufacturing estab-
lishments where nhrasives such as emery
aud diamond dust are In use. The new
substance II known as carbonupdum, and
H. the result ~ passing a strong currens
Of electricity through n mixture - pow
dered .carl,na and fine sand IN "A closed re-
tort
The chemist did not yet diamonds for
his trouble. but be may yet wear them, as
the new compound promises 10 prove very
valuable and may possibly supplant en-
cry In many commercial USES. Washing
Ton Post.