88 FROM NEBULA TO NEBULA 



It is obvious that if this explanation of tho earth's 

 rotation be true, the earth's axis must wobble some- 

 what, and the periods and variations of the movement 

 should be not only diurnal but monthly and annual as 

 well, thus affording the probable explanation of the 

 secular changes of latitude so laboriously investigated 

 and mapped by Prof. Chandler. 



It is no less obvious that the atmosphere ought to 

 be affected, though perhaps less noticeably, similarly to 

 the ocean. Accordingly, it is an observed fact that when 

 the water-tide is low the barometer is always higher 

 than normal. Heretofore this has been looked upon 

 merely as a coincidence, when as a matter of fact both 

 are due to the same law of tidal depression. Here, in 

 my opinion, is the chief cause of trade winds. 



It may be well to point out more clearly to those 

 who have not already followed up the applications in 

 their minds, just how a depression can cause high water, 

 and how the coincidence of high tide with the moon's 

 motion is explained. When the water is depressed in 

 the middle of the Pacific, say, by the noonday sun, the 

 water thus displaced must seek a passage round the 

 globe in all directions until stopped by the land. Now, 

 as the sun is always travelling westward it follows that 

 the water in front of it is being continually pursued 

 while the water behind it is being as gradually liber- 

 ated; so that the tides on the eastern coasts should be 

 both sharper and more severe. The moon's share in the 

 operation is to send tide- waves backward and forward 

 to those of the sun, and where they clash is the line of 

 "high tide." By gently blowing down upon the surface 

 of smooth water the reader can easily simulate the tidal 

 effect; and if two persons join in the experiment, the 

 action of both the sun and the moon can be fairly well 

 illustrated. The higher tides of our winters are plainly 



