Expedition, fcfc. 405 



posed, the yearly devastations of fires breaking out in dry 

 seasons, would destroy many of the trees. The forests being 

 thus broken, the growth of grasses and annual plants would 

 be greatly facilitated by the nakedness of the soil, and the 

 free admission of the rays of the sun. Forests attract rain, 

 and impede evaporation, while the reverberation from the 

 surface of vast plains, and deserts, tends to dissipate the 

 clouds and vapours which are driven over them by the winds. 

 In fertile districts like the alluvial lands of the Missouri and 

 Mississippi, a heavy annual growth of herbaceous plants is 

 produced, which, after the autumnal frosts, becomes dry and 

 peculiarly adapted to facilitate and extend the ravages of fire. 

 In a country occupied by hunters, who are kindling their 

 camp fires in every part of the forest, and who often, like 

 the Mongalls in the grassy deserts of Asia, set fire to the 

 plains, in order to attract herbivorous animals, by the growth 

 of tender and nutritious herbage which springs up soon after 

 the burning, it is easy to see these annual conflagrations 

 could not fail to happen. 



In the Autumn of 1819 the burnings, owing to the unusual 

 drought, continued until very late in the season, so that the 

 weeds in the low grounds were consumed, to the manifest 

 injury of the forests. Large bodies of timber are so frequent- 

 ly destroyed in this way, that the appearance has become 

 familiar to hunters, and travellers, and has received the name 

 of deadening. 



After the burning of the grass in the open prairies, the 

 wind, which, at that season, usually blows with great strength 

 from the northwest, carries off the ashes from the general 

 surface into the hollows and small vallies, thus contributing 

 to enrich the latter at the expense of the former.* 



The prairie appears to have heretofore extended almost 

 without interruption, for several miles in the rear of St. Lou- 

 is. The western portions of it are yet naked meadows, with- 



* See Wells On the Origin of Prairies, in the 4th number of Silliman's 

 Journal, 



