“Thus, from all we can learn respecting them, we may say that the Germans, during the first century before Christ, were fully prepared by their habits, laws, and their moral development, for a higher civilization. They were still restless, after so many centuries of wandering; they were fierce and fond of war, as a natural consequence of their struggles with the neighboring races; but they had already acquired a love for the wild land where they dwelt, they had begun to cultivate the soil, they had purified and hallowed the family relation, which is the basis of all good government, and finally, although slavery existed among them, they had established equal rights for free men. “If the object of Rome had been civilization, instead of conquest and plunder, the development of the Germans might have commenced much earlier and produced very different results.”—_Taylor._ [To be continued.] PHYSICAL SCIENCE. I.—THE AIR. When we begin to look attentively at the world around us, one of the first things to set us thinking is the air. We do not see it, and yet it is present wherever we may go. What is this air? Although invisible, it is yet a real, material substance. When you swing your arm rapidly up and down you feel the air offering a resistance to the hand. The air is something which you can feel, though you can not see it. You breathe it every moment. You can not get away from it, for it completely surrounds the earth. To this outer envelope of air, the name of _atmosphere_ is given. The air is not a simple substance, but a mixture of two invisible gases, called nitrogen and oxygen. But besides these chief ingredients, it contains also small quantities of other substances; some of which are visible, others invisible. If you close the shutters of a room, and let the sunlight stream through only one chink or hole into the room, you see some of the visible particles of the air. Hundreds of little motes, or specks of dust, cross the beam of light which makes them visible against the surrounding darkness, though they disappear in full daylight. But it is the invisible parts of the air which are of chief importance; and among them there are two which you must especially remember—the vapor of water and carbonic acid gas. You will soon come to see why it is needful for you to distinguish these.