244 LIGHT SCIENCE FOR LEISURE HOURS. 



it breeds the fogs infesting the path of the great stream 

 which flows from Vicksburg to Placquemines.' All 

 this is utter nonsense. The Mississippi has no more 

 to do with the great stream flowing through Louisiana 

 than with the Thames at London. The real Mississippi 

 is a stream of singular purity, and presents other charac- 

 teristics clearly recognisable as far as its junction with 

 the Missouri ; but in the stream which runs past St. 

 Louis none of the characteristics of the Mississippi can 

 be traced. Here, to all intents and purposes, the Mis- 

 sissippi comes to an end. As for the cause of the 

 motion of the great stream itself there can be little 

 question. Some have urged that it is due to the gra- 

 dual slope of the land; but in all the experimental 

 illustrations of the effects of such slope which we have 

 yet seen, the inclination has been monstrously exag- 

 gerated. If slope were the cause of the river's flow, 

 then unquestionably the effective part of the action 

 must reside in the Eocky Mountains, and not in the 

 great reaches of the river. We admit that the chief 

 bulk of the river lies in the great reaches ; but this 

 fact has no bearing, we assert, on the question at issue. 

 However, it is demonstrable that no cause of this sort 

 can be in question. For let the following reasoning 

 be carefully marked. In Wisconsin, in 40 north 

 latitude, the river partakes of the earth's rotation 

 motion, there equal in rate to about 800 miles per 

 hour; in Louisiana, in 30 north latitude, the river 

 still partakes of the earth's rotation movement, here 

 equal to about 900 miles per hour. Hence, were it 



