How to "merge" my Messages transcripts in OSX?

***EDIT: Perhaps a better way to say all of the below, is this: Is there a way to restore my Message (iChat) history onto my iMac, from my iCloud backup? All of my iDevices have the complete chat history, so this seems reasonable.*** Original post follows... My system got into a very weird state today, so I decided the best option was to restore to a new HD from a Time Machine backup. The last backup I had was from a month ago, but it restored fine. Now I have my new HD with 1-month old data, and my old HD with current data that I want to recover parts of. I found today's messages transcripts in ~/Library/Messages/Archive and I can view them just fine. But even after I added today's folder to my live Archive folder on the boot drive, Messages will not see the current chats at all. How can I "import" or "merge" or otherwise get my latest Messages transcripts to be blended in with the old ones?