Thanks for the Sansa Clip suggestion. It looks like I'll definitely have to buy a compatible device to listen to audible books because audible will not play on just any MP3 player. They're as protectionist and anti-competitive as Australian publishers.
No rock is completely impermeable, but some porous rocks like shale and pumice are mostly impermeable, because the pores are not interconnected, thus not allowing fluids or gases to pass through them. This is why shale makes a good cap-rock, and pumice floats instead of sinking.
A permeable membrane lets everything through, similar to how you let everyone into your home for the block party. An example of a permeable membrane in nature is the cell wall in plant cells.Cell walls provide support and protection for plant cells. They are fully permeable to water, molecules and proteins. This allows water and nutrients to be freely exchanged between the plant cells. permeable membrane lets everything through, similar to how you let everyone into your home for the block party. An example of a permeable membrane in nature is the cell wall in plant cells.