There is a popular notion that night air is unwholesome; but if you reflect that wholesome air is that which contains is full complement of oxygen, and no more than its very small complement of carbonic acid gas, and that all burning objects — fire, furnace, gas-lamp — give forth carbonic acid gas and consume oxygen, you will see that night air is, in ordinary circumstances, more wholesome then day air, simply because there is a less exhaustive drain upon its vital gas. When the children are out of a room which they commonly occupy, day nursery or breakfast-room, then is the opportunity to air it thoroughly by throwing windows and doors wide open and producing a thorough draft.