"I am going to show you a very pretty little filter now, made of blottingpaper. Teacher made some for the lesson. He gave me these to try with at home.
"See, there are three pieces of blottingpaper, cut round, and folded across the center at right angles. When I open them out, I can make a little funnel with them.
"Now I will stand the funnel in a tumbler, and pour into itsome of this chalk and water. See, the liquid looks thick and white like milk. Watch what happens when I pour it into the filter. Drop by drop, the water trickles through the pores of the blotting- paper. But it is clear water now. All the little pieces of solid chalk, that were floating in the water, are left behind in the blotting-paper. The blotting- paper is a filter. It filters the liquid I put into it."SUMMARY
Filters are made of porous substances. They let the clear water pass through their pores, but keep back the little pieces of solid matter. Blotting-paper is porous; it makes a good ?lter.
Lesson 05
The Poor Man"s Filter
"I say, Fred," said Willie, "shall we tell Norahabout the biggest filter in the world?"
"Oh yes, do, Fred." said Norah.