Logistics of keeping up on world events in the days of sailing ships

Factual Questions
1

I’m currently reading a book that is set in 19th-century Rio de Janeiro, and I came upon the following phrase:

“When the news of Napoleon’s first defeat reached Rio de Janeiro, …”

When I first read it, I simply accepted it without thought and went on to the rest of the paragraph. It wasn’t till later that I began to wonder about the ins and outs of worldwide news in those days.

Was the distribution of news to the New World formalized (e.g. a special “news officer” travelling on scheduled ships)?
Was it commonplace for ship’s captains to pick up the local newspaper and take it along for the trip, providing a “trusted source” for distant newspapers to quote?
Did people simply get their news from the grapevine?
Did news come in regularly, or in dribs and drabs?

Just how much would the cariocas in Rio have trusted that little nugget of info about Napoleon?

2

“Nothing important happened today” King George III’s diary, 4th July 1776.

3

Information was money than as now. Newspapers would be traded among ships and official dispatches would be sent by governments and corporations to their representatives abroad.

4

And news that this is a myth evidently travels even more slowly. George III never kept a diary. It was Louis XVI who wrote ‘Rien’ in his diary on 14 July 1789 (although he was actually referring to his lack of success while out hunting).

As DrFidelius says, news was valuable and local newspapers would be willing to pay for it. In the case of big stories, such as the defeat of Napoleon, the entire crew of the ship would know so the news would spread quickly on arrival anyway.