How does using a semicolon or a full stop change meaning?

Question

Federal agencies and Wal-Mart are investigating the charges; C. J.’s Seafood did not respond to The Times’s request for comment.

In this statement, what is the effect of semicolon in the meaning and what would the change in meaning be if we used full-stop (period) instead of a semi-colon?

I would like to know a general rule for how the meaning changes, how it would affect similar sentences, etc. If you know of tutorials on this subject, I'd be most grateful.

Answer 1

There's a lovely and beautifully self-demonstrating description of how punctuation marks work stylistically in Lewis Thomas's little piece on Punctuation.

Here's the paragraph on semicolons:

I have grown fond of semicolons in recent years. The semicolon tells you that there is still some question about the preceding full sentence; something needs to be added; it reminds you sometimes of the Greek usage. It is almost always a greater pleasure to come across a semicolon than a period. The period tells you that that is that; if you didn't get all the meaning you wanted or expected, anyway you got all the writer intended to parcel out and now you have to move along. But with a semicolon there you get a pleasant little feeling of expectancy; there is more to come; to read on; it will get clearer.

"The Greek usage" in the quotation refers to the fact (discussed in a previous paragraph) that

the Greeks employed the semicolon for their question mark. It produces a strange sensation to read a Greek sentence which is a straightforward question:

• Why weepest thou;

instead of

• Why weepest thou?

Answer 2

This is from Larry Trask’s 'Guide to Punctuation':

The semicolon (;) has only one major use. It is used to join two complete sentences into a single written sentence when all of the following conditions are met:
(1) The two sentences are felt to be too closely related to be separated by a full stop;

(2) There is no connecting word which would require a comma, such as and or but;

(3) The special conditions requiring a colon are absent.

I would say that the first of those conditions is not met in your example and that a full stop after charges would be a more effective way of separating the two clauses.