THE COLON
The conventional uses of the colon are not numerous. The following are the principal ones:
1. Between figures expressing the time of day in hours and minutes; but, as stated above, the period is used by some good printing-houses:
92. The train arrives at 6:20 P. M.
2. Between the name of a publisher and the place of publication, especially in title-pages and in book titles:
93. New York: The Macmillan Company.
3. After the salutatory phrase at the beginning of a letter, if not on the first line of the letter:
94. Dear Sir:
Your letter of the 21st ultimo is at hand.
When the salutatory phrase is put on the first line of the text of the letter, a comma and a dash is the usual punctuation:
94-1. Dear Mr. Smith,—Your letter of the 25th ultimo is at hand.