"Well," said Fred, "this cream is a mass of very tiny cells or bags of fat. Each cell is like a little bladder, with an extremely thin skin. In the dairy they skim off this cream to make butter.""Yes," said Norah, "but how do they make the butter, Fred?""The cream is put into a churn," said Fred. "The dairy-maid keeps ontur ning the handle to
shake the cream about. The object of shaking the cream is to break the thin skin of those little fat cells. When thelittle bladders break, the fat in them is set free, and forms into a solid lump of butter.""We saw something else in the milk." said Will. "I daresay Norah has often seen milk when it has turned sour.""Oh, yes," said Norah, "I saw some sour milk to- day. There was something white and thick and solid floating in it.""Well," said Willie, "teacher got some of this stuff out of the milk, by pouring a sour liquid called rennet into it.""But what did the rennet do to the milk?" said Norah.
"It made some of the milk form into white solid lumps," said Fred. "These lumps are called curds. The rest of the milk is known as whey.