[The Franchise]

This is from the book:

"All was well, until one day they met a thunderstorm—more than a thunderstorm, a thunder-battle. You know how terrific a really big thunderstorm can be down in the land and in a river-valley; especially at times when two great thunderstorms meet and class. More terrible still are thunder and lightning in the mountains at night, when storms come up from East and West and make war. The lightning splinters on the peaks, and rocks shiver, and great crashes split the air and go rolling in tumbling into every cave and hollow; and darkness is filled with overwhelming noise and sudden light. Bilbo ... saw that across the valley the stone-giants were out, and were hurling rocks at one another for a game, and catching them, and tossing them down into the darkness where they smashed among the trees far below, or splintered into little bits with a bang ... they could hear the giants guffawing and shouting all over the mountainsides."