Main Ideas from What You Heard

Why Swallows Leave

Swallows do not leave Britain because of the cold. They leave because of the insects. A swallow eats flying insects, and it catches them in the air. In October the insects disappear, and a bird that eats nothing else has to follow the food. So swallows fly to southern Africa: about six thousand miles, taking roughly six weeks. They travel by day and feed as they go. They lose about a third of their body weight on the way. Many do not arrive. The following spring they return, and a swallow will often nest in the very barn it hatched in.

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.