The animal merely makes a bed, which he warms with his body in a sheltered place; but man, having discovered fire, boxes up some air in a spacious apartment, and warms that, instead of robbing himself, makes that his bed, in which he can move about divested of more cumbrous clothing, maintain a kind of summer in the midst of winter, and by means of windows even admit the light and with a lamp lengthen out the day.