Citation? (I'm not asking because I doubt you, but because I want to use the information in future 2nd Amendment debates with the libbies in my office.)
Puckle's gun (the "Defence") was patented on May 15, 1718 at the London patent office. There is a mention of it in Ian Hogg's "Machine Guns" (should be available through Amazon). I would also be amazed if a google search didn't turn something up about it (if not, send a private message and I can e-mail you a photograph of it along with a short history).
The design presented to Congress was unrelated, and used an approach similar to the modern australian metalstorm gun (multiple charges and bullets loaded in the same barrel; reloading took a bit of time but the rate of fire was comparable to a modern machine gun, and the designer had plans for a "speedloader" using pre-loaded cartridge / magazine tubes). Congress did not see the utility of a repeating firearm, and chose not to fund its development (and thus the design faded into obscurity). It is generally ignored by the firearms history books, but if you know anyone with a subscription to American Rifleman who keeps them, go through their back issues (last page, "second shots" column sometime in the mid-1990s) and you should be able to find a small (paragraph or two) article on it; that is the only place I have seen it mentioned in print (maybe you can get some Freeper on the bang list who keeps back issues to volunteer for the research task).