54 CROSSING SWAMPS. 



The more ordinary cases of waggons and animals 

 becoming mired in sloughs and other swampy places, 

 we are hardly concerned with at present, though these 

 accidents are very common in all wild countries. In the 

 prairie region however, these spots are known under 

 the name of coulees, and consist very frequently of 

 blind watercourses, over-grown with reeds, and other 

 aquatic vegetation, situated at the bottom of depres- 

 sions, worn by the water to some depth below the 

 surface of the plain, which sometimes form very trou- 

 blesome obstacles. 



Extensive swamps are also occasionally met with, 

 quite impassable for animals and vehicles, apparently 

 consisting of chains of blind lakes, or lagoons, whose 

 waters have in like manner become grown over with 

 a thick mat of vegetation, which if once broken through, 

 may be found to cover a mass of soft mud and water, 

 of it is impossible to say what depth but passes are 

 sometimes found between these lakes, by which cara- 

 vans may cross, at spots where there are fords, with a 

 hard bottom. 



A still more curious class of country, and one which 

 is full of difficulties for the wayfarer, is that where the 

 surface of the plain is scored in all directions with 

 numerous ravines. These may be of almost any depth, 

 and are generally cut in the shape of the letter "V", 

 and though some are dry, generally there is a stream 

 flowing at the bottom, which after heavy rains becomes 

 a torrent. Some of these ravines are occasionally of 

 enormous dimensions and depth, descending abruptly 

 for perhaps one or two hundred feet or more below 

 the general level of the plain; and in the absence of 

 roads, should the banks be very precipitous, they pre- 



