Why do you think Edmund’s heart gave a giant leap?

Edmund's heart gave a giant leap when he cam to the conclusion that the lion was, in fact, a statue. Even though he was frightened, this realization gave him the courage to approach the lion.

Of course it must be only a statue! No living animal would have let itself get covered with snow. Then very slowly and with his heart beating as if
it would burst, Edmund ventured to go up to the lion. Even now he hardly dared to touch it, but at last he put out his hand, very quickly, and did. It was cold stone. He had been frightened of a mere statue!