The wing of a bird is an elastic, flexible organ, with a thick anterior and a thin posterior margin; hence the wing does not act like a solid board, but is thrown into a succession of curves. When a bird rises from the ground it leaps up with head stuck out and expanded tail, so that the body is in the position of a boy’s kite when thrown up. The wings are strongly flapped, striking forward and downward, and the bird quickly ascends. It has been shown that the wing describes a figure 8 in its action, the margin being brought down so that the tip of the wing gives the last blow after the part next the trunk has ceased to strike; hence, standing in front of a bird, the wing would be divided into two, the upper surface of one-half and the lower surface of the other being visible at the same time. These portions are reversed when the wing is drawn back and towards the body, before beginning another stroke; but it will be observed that during retraction the wing is still sloped, so that the resemblance to a kite is maintained. There are many varieties of flight among birds; of these the most remarkable is the sailing motion, in which the wings are but slightly moved. Probably the original impetus is maintained by the kite-like slope of the wing, and advantage may be taken of currents by a rotation of the wing at the shoulder, a movement invisible at any distance. The Story of the Big Redwood Trees[23] The “Big Trees” of California are the most magnificent specimens of tree growth that have ever been found. In addition, they are the oldest known living things; they connect the present with the past in a chain of living rings in the tree that betray their great age to the modern scientist. Estimates of the age of the “Big Trees” vary from the Christian Era through a period dating back beyond the coming of the Christian Saviour about 4,000 years. The “Big Trees” of California are known as the “Sequoias,” and they are divided into two different although closely related species. The few enormous trees of great age which are now preserved in groves are known as the _Sequoia Gigantia_. These big trees grow at an altitude between 4,000 and 7,000 feet, and, whether individual or in groves, they are found in protected valleys, canyons, etc. What is known as the Redwoods, or scientifically listed as _Sequoia Sempervirens_, grow in heavy stands and really are a younger growth of the “Big Trees.” The redwoods grow in the fog belt in the counties bordering the coast from Monterey Bay north to the Oregon line. These trees range in age from 500 to 2,000 years, and are generally supposed by the scientists to be a reproduction growth that began their earthly existence shortly after the glacial period. The _Sequoia Gigantia_ reproduce from cones, while the redwoods reproduce from suckers that grow from the stump. The redwoods bear non-fertile cones. Both species of the sequoias are evergreen.