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GEOGBAPHY. 



137 



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is it felt ? Does tlie river abound with eddies or whirl- 

 pools, and how are they occasioned? Do they inter- 

 fere with navigation or not ? Are they accompanied by 

 rocks or shoals ? Again, we must ascertain what fords a 

 river offers, and what depth of water is generally found 



over them : the nature of the bed of the river, particularly 



in the case of a ford, should also be carefully ascertained. 



In addition to these remarks, many other important 



peculiarities will often be 

 observer. In some countries, particularly in 

 limestone districts, the rivers are remarkable for their 

 subterranean courses.* Suddenly emerging in large 



disco 



vered bv the careful 



secondary 



volumes from the base of a lofty mountain, they flow 

 across rich alluvial plains, and are then as suddenly lost 

 in the cavities of another mountain, again to issue forth to 

 the light of day in a distant region, after their subterra- 



Nor should the traveller omit to notice, 



nean course. 



when crossing a river^ the direction in which it flows as 

 regards his own course, whether to the right or to the left. 

 Several distinguished travellers have been unable to con- 

 nect their observations from not having attended to this 



point. 



Sp 



•The phenomena connected with the out- 



bui-sts of water from the surface of the earth are not 

 only of the greatest interest, but a correct observation of 



them is attended with the greatest practical advantage. 

 The traveller should state, approximatively at least, their 

 size or volume, and the nature of the rock or soil out of 

 which they rise ; also whether they are pure or mineral, 

 and what deposits are formed about the orifices through 



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tyria and the neiglibouruood of Trieste. 



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