In another project, we built a very simple filter. Now, we will build one that is more complicated. It is also like some of the filters that nature built a million, zillion
years ago.

Let's start with a tall, glass tube that is open at both ends. We'll stand it up so that the bottom of it is in a glass bowl. We could even put three or four clean pebbles
under the tube to act as legs.

On the very bottom of the tube, we have taped some filter paper, and then put in several more layers of filter paper, and some cotton, so that the bottom filter is about one-half inch thick. Then, we'll pour in some charcoal that we got from the pet store where tropical fish are sold. (They use charcoal for the aquarium's filters.)

At the pet store, we also bought some small pebbles, and some sand. These items are used in the bottoms of aquaria. We'll put a two-inch layer of pebbles into our tube, and add about an inch of the sand.

Now, we'll make a really nasty-looking stuff called "charcoal paste." We grind up some of the charcoal we bought, and add water, mixing carefully, to make a paste. We'll put a layer of that stuff on top of the sand.

[Do you see how gross that charcoal paste looks? I think it is the same stuff they make you swallow at the hospital when you have eaten something poisonous. You better be careful not to eat things you haven't checked for edibility! Oh Yuck!]

The muddy water will be poured on top, and we'll watch it as it is filtered through the materials in our tube.

Look at the water in the bowl. Is it cleaner than the muddy water?

WE WILL NOT DRINK THIS WATER.

Leave it like it is, with the filtered water in the bowl under the tube. Remember, the bowl is like the water table or an aquifer.

Let's see what happens when we pour on some used motor oil (the kind that comes out of the car when Dad changes the oil).

OH, RATS! What have we done now? We have contaminated the soil AND the water table.

Will we ever find out what an aquifer is? There is one in Florida that underlies nearly the entire state!