If a cloud filled with one kind of electricity comes near the earth when the latter is filled with the opposite kind, the cloud may discharge its electricity to the earth. If any tall object, such as a tree, a steeple, or a house, happens to be near where the cloud discharges, the electricity will often pass down it to the earth. In this way houses are sometimes injured and set on fire and great trees are split up into small pieces. Sometimes, too, human beings and animals are struck and killed. It is not safe, therefore, to stand under a tree or close to a high house during a thunder storm.