CXXl 



their mouths, will simplify all the problems involved in the endeavor to 

 deepen the channels through them. 



A remarkable fact has been observed by savants, that the alteration of 

 river courses in consequence of the rotation of the earth, an influence which 

 would lead us to expect the continual erosion of the western bank of the 

 Mississippi, is neutralized here on account of a gradual upheaval of the 

 western chains of our continent, and the Mississippi system and likewise 

 the Texas system of rivers — in short, all the rivers that flow into the Gulf 

 of Mexico uniformly tend toward the southeast. This tendency is pro- 

 moted by the gradual subsidence going on in the Appalachian chain of 

 mountains. Whether these views are w^eil-founded or not, they serve to 

 call attention to the importance of noting the modification of local laws of 

 alluvial deposit by vastly extended surface upheavals and depressions. 

 The local action of the waves of the sea, of the oceanic currents, of the 

 tides, of the river freshets, must be studied, and, in addition to this, the 

 behavior of the entire river system revealing the slow but inevitable influ- 

 ence of terrestrial rotation and vast upheavals or depressions. 



When we look abroad upon Nature as presented to us by Science we re- 

 alize more and more fully the words of Humboldt in which he describes it as 

 a "whole moved and animated by internal forces," a vast process in which 

 even the "everlasting hills" seem to move and to perceptibly crumble away 

 under the disintegrating influence of the air and water. The gradual 

 contraction of the earth's crust effects a local upheaval or wrinkle, while 

 the perpetual process of the atmosphere undermines and levels all. 



Foremost upon our attention to-day, the means and appliances adopted 

 in the interest of the science of Meteorology force themselves. The esta- 

 blishment of the United States Signal Service and the daily collection and 

 publication of the results of the scattered observations is one of the great- 

 est events in the scientific world of to-day. Consider only how it has 

 cleared up the theory of storms. The valuable researches of Redfield, 

 Espy, Henry, Loomis, and Dov^, are complemented and reduced to har- 

 mony by the generalizations of the Signal Service. 



Cyclones are formed by the meeting of contrary winds. The grand 

 "battle-ground" on which our cyclones arise — and all storms are proven 

 to be cyclonic — is the circle of trade-wind influence, and this in summer is 

 between the loth and 12th parallels of North latitude. The tendency of the 

 southeast trade-winds to invade the territory of the northeast trade-winds 

 by sweeping over the equator into our hemisphere is the origin of cyclones, 

 according to Maury. All collisions of contrary winds tend to produce a 

 vortical whirl by reason of the influence of the revolution of the earth. A 

 wind blowing southward is deflected to the west, and one blowing north- 

 ward is deflect'^d to the east. Hence the movement of cyclones in the 

 Northern hemisphere is found to be opposite to the movement of the hands 

 of a clock, while in the Southern hemisphere the movement is the same 

 with the hands of a clock. Any vortical movement in the atmosphere, no 

 matter how slight, produces an ascending current of air, and this relieves 



