The Library of Congress is the largest library in the world in terms of shelf space, with over 30 million books. But it’s about to expand it’s holdings quite significantly — by 10 billion tweets and counting.

The New York Times has more on Twitter’s donation of its archives to the United States’ oldest federal cultural institution:

TWITTER users now broadcast about 55 million Tweets a day. In just four years, about 10 billion of these brief messages have accumulated.

Not a few are pure drivel. But, taken together, they are likely to be of considerable value to future historians. They contain more observations, recorded at the same times by more people, than ever preserved in any medium before.

“Twitter is tens of millions of active users. There is no archive with tens of millions of diaries,” said Daniel J. Cohen, an associate professor of history at George Mason University and co-author of a 2006 book, “Digital History.” What’s more, he said, “Twitter is of the moment; it’s where people are the most honest.”

The Library of Congress isn’t the only institution getting the tweets, though it’s the most scholarly.

The library will embargo messages for six months after their original transmission. If that is not enough to put privacy issues to rest, she said, “We may have to filter certain things or wait longer to make them available.” The library plans to dole out its access to its Twitter archive only to those whom Ms. Anderson called “qualified researchers.”

BUT the library’ s restrictions on access will not matter. Mr. Macgillivray at Twitter said his company would be turning over copies of its public archive to Google, Yahoo and Microsoft, too. These companies already receive instantaneously the stream of current Twitter messages. When the archive of older Tweets is added to their data storehouses, they will have a complete, constantly updated, set, and users won’t encounter a six-month embargo.