§ 531. THE GEOLOGICAL AGENCY OF THE WINDS. 285 



CHAPTEE XII. 



§ 531-555. — THE GEOLOGICAL AGENCY OF THE WINDS. 



531. Properly to appreciate the various offices which the winds 

 The sea and air re- aud the wavcs perform, wc iTLUst regard nature as 

 theslme'^LSine.^ a wholc, for all the departments thereof are inti- 

 mately 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 drift 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 specialty. The astron- 

 omer directs his telescope to the most remote star or to the near> 

 est planet in the sky, and* makes an observation upon it. He can 

 not reduce this observation, nor make any use of it, imtil he has 

 availed himself of certain principles of optics — until he has con- 

 sulted the thermoiiK ter, gauged the atmosphere, and considered 

 the effect of heat in changing its powers 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 he is to be led into 

 chambers where there are stores of knowleds^e and instruction es- 

 pecially for him. And thus, in undertaking to explore the phys- 

 ical 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 in considering marine fossils, changes of 



