THE GEOLOGICAL AGENCY OF THE WINDS. 285 



mucli Uglit 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 atten- 

 tive consideration, for it is the voice of Wisdom. 



CHAPTER XII. 



§ 531-555. — thp: 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 depart- 

 ment. 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 prin- 

 cijDles 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 w^eigh 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 lab^-rinth — all, 

 it may be, with different objects in view, but nevertheless, each 

 one feeling sure that ho is to be led into chambers where iliere 

 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 gealogist 

 on the land, and with him, far away from the sea-shore, engaged 



