The object of this book is to provide the beginner in the study of the earth's history with a general account of those actions which can be readily understood and which will afford him clear understandings as to the nature of the processes which have made this and other celestial spheres. It has been the writer's purpose to select those series of facts which serve to show the continuous operations of energy, so that the reader might be helped to a truer conception of the nature of this sphere th

The object of this book is to give the student who is about to enter on the study of natural science some general idea as to the conditions of the natural realm. As this field of inquiry is vast, it will be possible only to give the merest outline of its subject-matter, noting those features alone which are of surpassing interest, which are demanded for a large understanding of man's place in this world, or which pertain to his duties in life. In entering on any field of inquiry, it is most desi

It is desirable that the student of Nature keep well in mind the means whereby he is able to perceive what goes on in the world about him. He should understand something as to the nature of his senses, and the extent to which these capacities enable him to discern the operations of Nature. Man, in common with his lower kindred, is, by the mechanism of the body, provided with five somewhat different ways by which he may learn something of the things about him. The simplest of these capacities is

Although little is known of the motions which occur among the celestial bodies beyond the sphere of our solar family, that which has been ascertained is of great importance, and serves to make it likely that all the suns in space are upon swift journeys which in their speed equal, if they do not exceed, the rate of motion among the planetary spheres, which may, in general, be reckoned at about twenty miles a second. Our whole solar system is journeying away from certain stars, and in the directi

We have seen that the matter in the visible universe everywhere tends to gather into vast associations which appear to us as stars, and that these orbs are engaged in ceaseless motion in journeys through space. In only one of these aggregations—that which makes our own solar system—are the bodies sufficiently near to our eyes for us, even with the resources of our telescopes and other instruments, to divine something of the details which they exhibit. In studying what we may concerning the famil

Before the use of the telescope in astronomical work, which was begun by the illustrious Galileo in 1608, astronomers were unable to approach the problem of the structure of the sun. They could discern no more than can be seen by any one who looks at the great sphere through a bit of smoked glass, as we know this reveals a disklike body of very uniform appearance. The only variation in this simple aspect occurs at the time of a total eclipse, when for a minute or two the moon hides the whole bod

In beginning the study of the earth it is important that the student should at once form the habit of keeping in mind the spherical form of the planet. Many persons, while they may blindly accept the fact that the earth is a sphere, do not think of it as having that form. Perhaps the simplest way of securing the correct image of the shape is to imagine how the earth would appear as seen from the moon. In its full condition the moon is apt to appear as a disk. When it is new, and also when in its

In the region near the equator, or near the line of highest temperature, which for various reasons does not exactly follow the equator, there is, as we have noticed, a somewhat continuous uprushing current where the air passes upward through an ascending chimney, which in a way girdles the sea-covered part of the earth. In this region the movements of the air are to a great extent under the control of the great continuous updraught. As we go to the north and south we enter realms where the air a

The envelope of air wraps the earth completely about, and, though varying in thickness, is everywhere present over its surface. That of the waters is much less equally distributed. Because of its weight, it is mainly gathered in the depths of the earth, where it lies in the interstices of the rocks and in the great realm of the seas. Only a very small portion of the fluid is in the atmosphere or on the land. Perhaps less than a ten thousandth part of the whole is at any one time on this round fr

The system of ocean currents, though it exhibits much complication in detail, is in the main and primarily dependent on the action of the constant air streams known as the trade winds. With the breath from the lips over a basin of water we can readily make an experiment which shows in a general way the method in which the winds operate in producing the circulation of the sea. Blowing upon the surface of the water in the basin, we find that even this slight impulse at once sets the upper part in

We have now to consider those movements of the water which depend upon the fact that at ordinary temperatures the sea yields to the air a continued and large supply of vapour, a contribution which is made in lessened proportion by water in all stages of coldness, and even by ice when it is exposed to dry air. This evaporation of the sea water is proportional to the temperature and to the dryness of the air where it rests upon the ocean. It probably amounts on the average to somewhere about three

We turn now to the geological work which is performed by falling water. Where the rain or snow returns from the clouds to the sea, the energy of position given to the water by its elevation above the earth through the heat which it acquired from the sun is returned to the air through which it falls or to the ocean surface on which it strikes. In this case the circuit of the rain is short and without geological consequence which it is worth while to consider, except to note that the heat thus ret

In considering the journey of water from the hilltops to the sea, we should take some account of those pauses which it makes on its way when for a time it falls into the basin of a lake. These arrests in the downward motion of water, which we term lakes, are exceedingly numerous; their proper discussion would, indeed, require a considerable volume. We shall here note only the more important of their features, those which are of interest to the general student. The first and most noteworthy diffe

We have already noted the fact that the water in the clouds is very commonly in the frozen state; a large part of that fluid which is evaporated from the sea attains the solid form before it returns to the earth. Nevertheless, in descending, at least nine tenths of the precipitation returns to the fluid state, and does the kind of work which we have noted in our account of water. Where, however, the water arrives on the earth in the frozen condition, it enters on a rôle totally different from th

Of old it was believed that volcanoes represented the outpouring of fluid rock which came forth from the central realm of the earth, a region which was supposed still to retain the liquid state through which the whole mass of our earth has doubtless passed. Recent studies, however, have brought about a change in the views of geologists which is represented by the fact that we shall treat volcanic phenomena in connection with the history of rock water. In endeavouring to understand the phenomena

The frequent mention which it has been necessary to make of soil phenomena in the preceding chapters shows how intimately this feature in the structure of the earth is blended with all the elements of its physical history. It is now necessary for us to take up the phenomena of soils in a consecutive manner. The study of any considerable river basin enables us to trace the more important steps which lead to the destructure and renovation of the earth's detrital coating. In such an interpretation

In ordinary experience we seem to behold the greater part of the earth which meets our eyes as fixed in its position. A better understanding shows us that nothing in this world is immovable. In the realm of the inorganic world the atoms and molecules even in solid bodies have to be conceived as endowed with ceaseless though ordered motions. Even when matter is built into the solid rock, it is doubtful whether any grain of it ever comes really to rest. Under the strains which arise from the contr

Although it is beyond the power of man to conceive any such lapses of time as have taken place in the history of this earth, it is interesting, and in certain ways profitable, to determine as near as possible in the measure of years the duration of the events which are recorded in the rocks. Some astronomers, basing their conclusions on the heat-containing power of matter, and on the rate at which energy in this form flows from the sun, have come to the conclusion that our planet could not have

Set over against the earth—related to, yet contrasted with it in many ways—the moon offers a most profitable object to the student of geology. He should often turn to it for those lessons which will be briefly noted. In the beginning of their mutual history the materials of earth and moon doubtless formed one vaporous body which had been parted from the concentrating mass of the sun in the manner noted in the sketch of the history of the solar system. After the earth-moon body had gathered into

So far as possible the preceding pages, by the method adopted in the presentation of facts, will serve to show the student the ways in which he may best undertake to trace the order of events exhibited in the phenomena of the earth. Following the plan pursued, we shall now consider certain special points which need to be noted by those who would adopt the methods of the geologist. At the outset of his studies it may be well for the inquirer to note the fact that familiarity with the world about