Main Idea and Key Details

The Salmon's Return

A salmon hatches in a river, swims to the sea, and comes back years later to the river it was born in. It finds its way home by smell. Every river carries its own mixture of soil, rock and plants, and a young salmon learns that smell before it leaves. The return journey is upstream. The fish leap waterfalls, sometimes several metres high, and they do not eat once they enter fresh water. Because it is not feeding, a salmon uses up its own body on the climb. By the time it reaches the gravel where it hatched, it is thin and worn. There it lays its eggs. Most Atlantic salmon die soon afterwards.

Turning Milk into Cheese

Cheese begins as an accident that people learned to repeat. Milk is mostly water with fat and protein in it. To make cheese, the protein has to be separated out. A starter culture of bacteria is added first. The bacteria turn some of the milk sugar into acid, and the acid begins to make the protein clump together. Then rennet is added, which finishes the job. The milk splits into solid curds and watery whey. The whey is drained off. The curds are pressed, salted, and left to age. Time does the rest: a cheese aged for two years tastes nothing like the same cheese at two weeks.