Some ignorant persons, in all ages of the world, have fancied that the relative positions of the stars to each other, at the moment of the birth of an individual, must have an influence upon his character and the future circumstances of his life. Thus arose what was called the _science_ of astrology, and the practice of _casting nativities_; and in vulgar conversation it is not unfrequent for people, who do not know the origin of the expression, to "thank their stars," or to talk of their "unlucky stars," which arose from the prevalence of such a belief. This, I need hardly tell you, is all nonsense, from beginning to end; but you may now know that there is, in reality, quite as wonderful a connection, and as direct a one, between yourselves and the stars, as this which was fancied to exist. VIII. But who can tell how wide the relationship of our earth and everything upon it is extended, through the agency of those wonderful principles Light, Heat, and Electricity? It may seem to you impossible, when I tell you that there is not a blade of grass or a flower on this earth, which may not, in its little degree, affect the climate of a star far beyond the limits of our solar system; but if you will consider the way in which the falling of dews is regulated, you will see that there are grounds for such a notion. I must first tell you that it is a property of Heat, like Light, to _radiate_ or expand itself in all directions, without limit; so that a heated body is always sending out its heat. Now, this radiation is influenced by the surfaces of bodies: Heat will radiate more from a black rough surface than from a smooth white one, and a black body will therefore much sooner get cool than a white one, as I had occasion to tell you just now. The heat radiates rapidly from the leaves of vegetables, though from different kinds of plants in very different degrees, while from stones and dry wood it radiates very slowly. Heat is also _reflected_, or turned back, by meeting with certain objects; and in this respect, too, it resembles light. You have possibly seen experiments showing this, made with polished metal mirrors. At night time, when the sun's rays are not present, as the heat radiates quickly from the plants on the ground, each plant becomes thereby cooler than the earth and stones which surround it. This causes the watery particles which the air contains, to condense on its leaves and flowers, in the same manner as you see the moisture in the air of a crowded room, settle on the outside of a glass of cold water; and, what is most wonderful, the surface of each plant is so constructed as to allow the escape of just so much heat, and to receive just so much dew in return, as its peculiar nature requires. You may see, if you look, that some plants always have more dew on them than others.