Main Idea and Key Details

How Braille Was Invented

Louis Braille was blinded in an accident at the age of three. At his school, blind pupils read by tracing raised letters pressed into paper. It worked, slowly — a fingertip cannot take in a whole letter shape at once — and nobody could write that way at all. When Braille was twelve, a soldier visited the school with a code of raised dots that soldiers used to read messages in the dark. It was too complicated, but the idea of dots was right. Braille spent three years simplifying it. He settled on a cell of six dots, small enough to sit under one fingertip. He was fifteen when he finished. He was forty-three when he died, and the system was not widely accepted until after that.

How a Windmill Grinds Flour

A windmill turns moving air into turning stone. The sails are set at a slight angle. Because of that angle, wind pushing on them cannot pass straight through, so it pushes them round instead. The sails turn a horizontal shaft. A large wooden gear on that shaft meshes with a smaller one on an upright shaft, which turns the millstones below. Because the smaller gear has fewer teeth, it spins faster than the sails do. Four turns of the sails can mean twenty turns of the stone. The grain falls between two stones. The top stone turns; the bottom one does not. The grain is crushed between them, and flour comes out at the edge.