What is the most effective design for an infinite cobblestone generator?

I have one lava and one water. I want to make stone factory, which is:

  • the most compact
  • the most safe to get stone from it

To me, the most compact design would be 6x3x3. It is very simple and can be constructed from nearly anything. There is an approximate 50% yield. Here is a video of what I mean


I use the design in this post on the Minecraft forums (requires forum account). The design is also shown in this video.

You say you only have one water, but I'm sure it's not too difficult to get another. This generator allows you to mine two blocks, moving your cursor back and forth (so you're not just holding left-click for hours). The water currents will bring the dropped cobblestone towards the block on which you stand. It takes up 5x5x3 blocks of space, and if you build it in a corner of a building, you can omit the leftmost column and top row, diminishing the size to 4x4x3.

To build it, construct the following:

BOTTOM  MIDDLE   TOP  │  KEY
                      │  
█████   █████   █████ │  █ - generator body (solid material)
███.█   ███W█   █████ │  W - water source
███.█   ██.▒█   ██L██ │  L - lava source
█...█   █W▒..   ███.. │  ▒ - cobblestone that is generated
████.   ███..   ███.. │  . - empty block
    ↑       
stand
 here

And the video showing it:


On top of that, add a piston behind where the cobblestone is generated, and have it powered by redstone pulses. to do that, place 3 redstone repeaters one direction and 3 the opposite direction beside the first 3, and wire them together at the ends. now add a lever (not a button) to one side of the circuit and very quickly turn it on and off once. the piston will push out each block of cobblestone into a row of 12. you can then add pistons in a very similar design along that row, to make a square. then, if you're really adventurous and have time on your hands, put a third piston circuit at the opposite end of that square with the pistons pushing up in pulses all the time. this will create a wall which regenerates itself. cheerio.