In your reading for material do not cultivate habits of economy or
parsimony. You should always have a considerable amount of good fact
left over, for unless you know a good deal of the region on the
outskirts of your argument you will feel cramped and uncertain within
it. The effect of having something in reserve is a powerful, though an
intangible, asset in an argument; and, on the other hand, the man who
has emptied his magazine is in a risky situation.

13. Sources for Facts. In the main, there are two kinds of sources
for facts, sources in which the facts have already been collected and
digested, and sources where they are still scattered and must be brought
together and grouped by the investigator. Obviously there is no sharp or
permanent distinction between these two classes. Let us first run
through some of the books which are commonly available as sources of
either kind, and then come back to the use of them.

To find material in books and magazines there are certain well-known
guides. To look up books go first to the catalogue of the nearest
library. Here in most cases you will find some sort of subject
catalogue, in which the subjects are arranged alphabetically; and if you
can use the alphabet readily, as by no means all college students can,
you can soon get a list of the books that are there available on the
subject. On many subjects there are bibliographies, or lists of books,
such as those published by the Library of Congress; these will be found
in every large library. For articles in magazines and weekly journals,
which on most current questions have fresh information, besides a great
deal of valuable material on older questions, go to Poole's "Index to
Periodical Literature," which is an index both by title and subject to
the articles in important English and American magazines from 1802 to
1906, and to "The Reader's Guide to Periodical Literature," which began