much light on the features and character of the clouds in different latitudes and seasons. Physical facts are the language of Nature, and every expression uttered by her is worthy of our most attentive consideration, for it is the voice of Wisdom.
CHAPTER XII.
§ 531-555.—THE GEOLOGICAL AGENCY OF THE WINDS.
531. The sea and air regarded as parts of the same machine.—Properly to appreciate the various offices which the winds and the waves perform, we must regard nature as a whole, for all the departments thereof are intimately connected. If we attempt to study in one of them, we often find ourselves tracing clews which insensibly lead us off into others, and before we are aware, we discover ourselves exploring the chambers of some other department. The study of drifts takes the geologist out to sea, and reminds him that a knowledge of waves, winds, and currents, of navigation and hydrography, are closely and intimately connected with his speciality. The astronomer directs his telescope to the most remote star or to the nearest planet in the sky, and makes an observation upon it. He cannot reduce this observation, nor make any use of it, until he has availed himself of certain principles of optics—until he has consulted the thermometer, gauged the atmosphere, and considered the effect of heat in changing its powders of refraction. In order to adjust the pendulum of his clock to the right length, he has to measure the water of the sea and weigh the earth. He, too, must therefore go into the study of the tides; he must examine the earth's crust, and consider the matter of which it is composed, from pole to pole, circumference to centre; and in doing this, he finds himself, in his researches, alongside of the navigator, the geologist, and the meteorologist, with a host of other good fellows, each one holding on by the same thread, and following it up into the same labyrinth—all, it may be, with different objects in view, but nevertheless, each one feeling sure that ho is to be led into chambers where here are stores of knowledge and instruction especially for him. And thus, in undertaking to explore the physical geography of the sea, I have found myself standing side by side with the geologist on the land, and with him, far away from the sea-shore, engaged
