LEVEL OF RIVER AND OCEAN. 



91 



add, that the reverse takes place under opposite circumstances. 

 Some persons attribute this change of level to the horizontal 

 action of wind ; but I am inclined to think it occasioned chiefly 

 by vertical pressure of the atmosphere, increased, doubtless, 

 during strong winds by their driving force. 



Before a pampero, the barometer continues to fall during 

 several days, and invariably the water then rises. The gale 

 commences, the barometer ceases falling and begins to rise, and 

 very soon afterwards the level of the river is found to be sink- 

 ing. For many following days the glass remains high, but the 

 water continues to fall, and, generally speaking, the river is 

 low while the mercury is steady and above the average height, 

 which I should consider to be ^9*9 inches. In the Plata I 

 never saw the barometer higher than 30-3, nor lower than 

 S9*4. ^ I will not delay here to speak of corresponding ele- 

 vations or depressions of the ocean at other parts of the South 

 American coast, and attempt to trace out the effects of gales in 

 high latitudes, the space through which those winds extend, 

 and whether they reach or affect places in a low or even middle 

 latitude ; but leaving such inquiries for another place, take a 

 few more glances at the vicinity of the Plata, and then con- 

 tinue the narrative. 



Having already noticed the width and average shallowness 

 of this immense river, and the lowness of its adjacent shores, I 

 need only add, that on the northern side there is a sprinkling 

 of hills, of a granitic structure, scattered amidst extensive 

 plains, while on the south, or right bank, there is neither a 

 hill, a rock, or even a stone.-[- So low is the land between 

 Point Piedras and Cape San Antonio, that around the great 

 bay, called Sanborombon, it is extremely difficult to say where 

 the water ends, or the coast line begins. Each difference, of 



• In estimating' weather, or force of wind, by the heig-ht of the mer- 

 curial column, due reg-ard should be had to the goodness of the 

 instrument, as some barometers, used in ships, dilfer from others even 

 tenths of an inch. 



t Which has not been carried there by man, or by running water. 



