+512.+ The colon is not used as much as it formerly was. The comma and
the semi-colon and the period are now used in most of the places where
older writers used the colon.
One authority in English says that, "in strict logic the colon is to the
sentence in which it is used what the mark of equality is in
mathematics."
+513.+ The colon is used before a formal list of items. For example:
Economics has three important divisions: production, distribution,
consumption.
+514.+ The colon is used after a salutation at the beginning of a
letter. For example: _Dear Sir:_ _Gentlemen:_ _Comrades:_
In such cases the dash is also frequently used with the colon. For
example: _My dear Sir:--_ _Gentlemen:--_ _Comrades:--_
+515.+ The colon is more often used instead of the semi-colon after such
expressions as, _thus:_ _as follows:_ _the following:_ _for example:_
etc.
The colon is also used to separate a series of sentences which are
explanatory of the main clause. For example:
The People's College has two great aims: the first is to bring
education within the reach of every worker; the second is to teach
from the viewpoint of the working class.
We were advised to proceed thus: first, to be systematic in our work;
second, to concentrate; third, to go slowly and surely; and last of
all, to think for ourselves.