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Dewey and decimals

Ah--Dewey is an amazing and complex system.  When you consider that is is
a way to try to organize the entire range and depth of human knowledge it
is hardly surprising that it is not a simple system.

You asked about how to get to the third digit beyond the decimal point.
But the numbers don't work quite that way, which means that logical
breaking points may or may not come at that point.  If you care to follow
I can give an example.

Someone mentioned the tables.  The geographic tables go from general to
specific.  An example
7   North America
73  United States
798 Alaska (Various states and regions have different numbers
            all starting with 7 since  there are so many)
7982 Southeast Alaska

The numbers from the geographic tables are appended to numbers from the
general schedules (the formal term for the basic list of numbers.  The
900's are history and geography.  or more specifically 9 for history and
91 for geography.  Thus

970  History of North America
973  History of the United States
979.82  History of Southeast Alaska

917  Geography of North America
917.3  Geography of the United States
917.982  Geography of Southeast Alaska

First you build the number, then you count over three places and put in
the decimal.  Some numbers can just have the geographic table numbers
stuck on.  The schedules tell you this.  Other times there is a code that
is inserted which tells you that the numbers that follow are geographic.
The index to my Deweymanual says that book binding is 686.3.  If someone
wrote a book about binding in Southeast Alaska and you wanted to sort it
geographically it would be 686.3'09'7982.  It would be written without
the little marks separating the sections.

It is a challenge to try to explain this in a few coherant words.  The
best introduction I know of is in the front of the Sears list of subject
headings which is often used by school and small libraries.  The Dewey
classification books which are used in medium sized libraries are four
fat volumes.  Large libraries tend to use the Library of Congress
Classification system.  Dewey can describe anything, but as you can see
from the examples above, the numbers can get very long.  LC uses a
combination of letters and numbers and thus has more groups to sort
things in.

Good luck.  I can remember wondering the same thing before I went to
library school.

Joyce Jenkins
Petersburg Public Library
In Southeast Alaska 917.982

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