276 ON THE NATURE AND HISTORY 



country,) they effected, without suffering any diseases but the 

 ordinary ones of the bivouac ; and in June advanced again to- 

 wards Spain in a healthy condition, during very hot weather. 

 The army was still healthy, certainly without endemic fever, 

 and marching through a singularly dry rocky country, of con- 

 siderable elevation, on the confines of Portugal. The weather 

 had been so hot for several weeks as to dry up the mountain- 

 streams ; and in some of the hilly ravines, that had lately been 

 water-courses, several of the regiments took up their bivouac, 

 for the sake of being near the stagnant pools of water that 

 were still left amongst the rocks. The Staff Officers, who had 

 served in the Mediterranean, pointed out the dangerous na- 

 ture of such an encampment ; but as its immediate site, 

 amongst dry rocks, appeared to be quite unexceptionable, 

 and the pools of water in the neighbourhood perfectly 

 pure, it was not changed. Several of the men were seized 

 with violent remittent fever before they could move from the 

 bivouac the following morning ; and that type of fever, the 

 first that had been seen on the march, continued to affect that 

 portion of the troops exclusively for a considerable time. Till 

 then it had always been believed amongst us, that vegetable 

 putrefaction (the humid decay of vegetables), was essential to 

 the production of pestiferous miasmata ; but, in the instance 

 of the half-dried ravine before us, from the stoney bed of 

 which, (as soil never could lie for the torrents,) the very exist- 

 ence even of vegetation was impossible j it proved as pestife- 

 rous as the bed of a fen. The army advanced to Talavera 

 through a very dry country, and in the hottest weather fought 

 that celebrated battle, which was followed by a retreat into the 

 plains of Estremadura, along the course of the Guadiana river, 

 at a time when the country was so arid and dry, for want of 

 rain, that the Guadiana itself, and all the smaller streams, had 



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