4" 



2S6 NOTES ON BRAZIL. 



carried with it that of the lesser lake, and formed the Rio Grande, 

 whose bar is still proceeding Southward. 



At first the Estuary must consist of a number of pools, sometimes 

 dry, and sometimes formed into one by an increase of water. Some of 

 them would, by degrees, collect in their bottoms a quantity of mud, 

 which, itself accumulating, and aided by the flying sand, would, at 

 length, fiU them up. Remnants of such lakes exist along both the 

 peninsulas, and the frequent existence of clay beneath the sand is, to me, 

 an evidence that they were once numerous. Had marine or fresh water 

 vegetables been growing there, they would have been buried, but not 

 destroyed, and, perhaps, in the course of ages, have been converted into 

 different kinds of coal. 



The manner in which the sand is urged forward by violent South- 

 Easterly winds, has been already stated ; and, indeed, if there be any 

 wind at all, the smaller particles may always be observed in progress. 

 More clearly to ascertain the effects produced in this way, I frequently 

 laid down pieces of wood or lumps of clay, stuck up a dry bush, and 

 dug holes in the sand ; and, in a few hours, a line has been formed under 

 the shelter of such substances, and the holes filled up. If the wind was 

 gentle, the ridges were formed on one side only ; if strong, a mass was 

 accumulated all around. I have been astonished to see how soon a hil- 

 lock was formed which buried the impeding article, and all traces of a 

 considerable hole obHterated. The continual advancement of the hills 

 once formed, is illustrated by that mass of sand which has been mentioned 

 as existing near the church of St. Pedro. It has been fifty years in 

 accumulating, as old people tell us, and its elevation is such as to indicate 

 that it must have risen about a foot every year. 



My observations on this particular hillock will serve, al^, to throw 

 some light on the adhesion of the loose materials of which the neigh- 

 bouring deserts are composed. Its encroachment on the street occasioned 

 many men to be employed in clearing it away ; and it was matter of no 

 small surprise to me that, as they worked at the bottom, the heap did 

 not slide downward, but the face of it remained nearly perpendicular. 



