Today, we will go over how to make an easy cobble generator. To start, you need: 1 bucket of lava, 1 bucket of water, some dirt, a piston, some redstone, some mine cart tracks, powered rails, a detector rail, redstone torches, and a lever. 

This device is not as confusing as some you can make. To start, when a non base water and non base lava block touch, it creates a cobble stone block. Then, the piston pushes the cobble out, so a new one can form. The piston gets activated by the never ending mine cart that keeps going around and around. That is why you need the detector rail. The lever is there so you can stop it when needed.