CONTENTS xi Luminous Bodies.- Transparent and Opaque Bodies.- Light and Its Properties. Images through Small Openings.- Shadows.- Brightness or Intensity of Light.- Candle Power.- Exercises.- Division of Light Striking a Body.- Reflection of Light.- Mirrors.— Dispersed or Diffused Light.- Refraction of Light.- The Lens.- Composition of White Light.- The Rainbow.- Absorption of Light; Color. The Sky and Its Colors.- Change of Light into Heat.- Light and Life. Exercises. Simple Microscope.- Compound Mi- croscope. The Camera.- How Sounds are Made and Carried.- Need of Machines.- Law of Machines.- The Lever.- Classes of Levers. Exercises.- Pulleys.- Wheel and Axle.- Inclined Plane. Acids. Classes of Acids. Acids and Coloring Matter.- Action of Acids with Metals.- Action of Acids with Carbonates.- Alkalies Modern Conveniences.- Water Supply.- Plumbing.— Hydrants and Traps. Kindling a Fire; Matches.- The Fireplace.- Stoves.- Causes of Weather.- Changes in Density and Pressure of Air.- Heating of the Air.- Moisture of the Air.- Humidity.- Dew and Frost. Fogs and Clouds. Forms of Clouds.- Rain and Snow. - Hail.- Rainfall.- Exercises. The Winds. Regular Win ds.- Storms and Cyclones.- Thunderstorms.- Tornadoes.- Cyclones of The Earth's Crust.- Some Common Rocks.- Classes of Rocks.- Origin of Stratified Rocks.- Origin of Igneous and Metamorphic - Bean. Other Seeds. Leaves.- Work of Leaves. Modified What is an Animal?— One-Celled Animals.— Simple Many-Celled Animals. Starfishes.- Worms. Mollusks.- Crustaceans.- In- Chief Divisions of the Body.-Cells and Tissues of the Body.— Structure of Bones.- Joints.- The Skeleton.- Muscles and Tendons. Circulation of the Blood.- The Heart.- - Arteries and Veins.- Capillaries. Blood.- Lymph. Excretion. Respiration. The The Nervous System.- Nerve Cells and their Structure.- Brain and its Parts.- Spinal Cord.- Sympathetic System.- Nervous System as a Whole.— Voluntary and Involuntary Action.— Reflex Action.- Habit. Effect of Alcohol and Tobacco on the Nerves.— Exercises. The Special Senses.- Touch.- Taste.- Smell. Hear- ing; Structure of the Ear.- Sight.- Eye Socket and Lids.- Parts of Bacteria and their Relation to Disease.- - How the Body Resists Bacteria. Natural Destruction of Germs.- Artificial Destruction - THE FIRST YEAR OF SCIENCE CHAPTER I MATTER AND ITS MEASUREMENT 1. The Earth and Science. In order that we may get a knowledge of the earth we must study the separate parts that make it up. We have already done this somewhat in Geography. Hence we know that the earth consists of many different rocks and soils, trees and plants; of bodies and streams of water; of the air; of a multitude of animals that live on or in the soil, the vegetation, and the water. We call any particular rock, tree, lake, or animal an object, or body. The sum of all its objects, large and small, is the earth itself. Nature, or the Universe, includes the earth together with the sun, moon, stars, etc. Science is the study of the truth about the objects of nature. Since the number of objects is very large, one method of studying nature is to find important resemblances and differences between objects. We can then arrange objects in groups or classes. Thus, we can make a division of all objects into (a) living objects and (b) non-living objects. Living things may then be classified as either animals or plants. Plants in their turn may be |