hought. Each sentence
takes a meaning because of its relation to some other. The personal
pronouns and pronominal adjectives, adverbial phrases indicating time or
place, conjunctions, and such expressions as _certainly, however, on the
other hand_, etc., are used to indicate more or less directly a relation
in thought between the phrase or sentence in which they occur and some
preceding one. If the reader cannot readily determine to what they refer,
the meaning becomes obscure or ambiguous. The pronominal adjectives and
the personal pronouns are especially likely to be used in such a way as to
cause ambiguity. Care must be taken to use them so as to keep the meaning
clear, and your own good sense will help you in this more than rules.
Notice in your reading how frequently expressions similar to those
mentioned above are used.

+Theme XVII.+--_Write a theme suggested by one of the following
subjects:_--

1. The last quarter.
2. An excursion with the physical geography class.
3. What I saw while riding to town.
4. The broken bicycle.
5. An hour in the study hall.
6. Seen from my study window.

(Are your sentences so arranged that the relation in thought is clear? Are
the personal pronouns and pronominal adjectives used so as to avoid
ambiguity? Does your story relate real events or imaginary ones? If
imaginary events are related, have you made them seem probable?)

+37. Getting the Main Thought.+--In many cases the relation in thought is
not directly indicated, and we are left to determine it from the context,
just as we decide upon the meaning of a word because of what precedes or
follows it. In this case the meaning of a particular sentence may be made
clear if we have in mind the main topic under discussion. Many pupils fail
in recitations because they do not distinguish that which is more
important from that which is less so. If a dozen pages of history are
assigned, they cannot master the lesson because it is too long to be
memorized, and they are not able to select the three or four things of
importance with which it is really concerned. Thirty or forty minor
details are jumbled together without any clear knowledge of the relations
that they bear either to one another or to the main thoughts of the
lesson.

In the following selection but three things are discussed. Determine what
they are, but not what is said about them.

In all the ages the extent and value of flood plains have been incr