- 4 — 



taken during a month in a period of low waters, which 

 was noteworthy for its duration — from the end of Decem- 

 ber 1900 to the end of May, of the present year — to deter- 

 minate approximately the general slope of the river. 



To arrive at this result, the observations of February 

 of this year have been selected because the river during 

 this month did not undergo variations of importance in 

 its discharge, the changes in height at the gauges be- 

 tween Nueva Palmira and the Estancia Humaita being 

 solely caused by the propagation of the tides. 



SupjDOsing the geometric place of the high tides to 

 be a horizontal line, which may be admitted in the 

 case of a river having a small slope, the average of the 

 maxima observed at the gauges has been taken as ordi- 

 nates in a downward direction and joining up the ends 

 of the ordinates obtained in this manner, the relation of 

 the zeros (planes of reference) at the different gauges 

 has been found, which has allowed to refer them to that 

 of Nueva Palmira (which is 0.28 mts. below the zero 

 plane of reference of the Riachuelo). 



The result of this operation is that the zero of the 

 gauge of the Island of Sauzal, Banco Grande and Uru- 

 guay appear to be 40,53 and 54 centimetres respectively 

 above that of the gauge of Nueva Palmira ( Sheet N°. IV). 



The average minimum for each gauge has also been 

 taken and by locating the resulting heights with regard 

 to the zeros of the gauges, the geometric place of the 

 low tides corresponding with the observed oscilations has 

 been established, which mean amplitude in this manner 

 has been determined for each gauge. 



By establishing the relation of the zero (plane of re- 

 ference) at the different gauges erected as far as the 

 Estancia Humaita ( in front of Guaviyu R. 0.) as well as 

 by a direct levelling over a distance of 14.350 mts. be- 

 tween the estancia Humaita and Nueva Escocia, and by cal- 

 culating the slope of the river supposing the existance of a 

 mean velocity of 0.15 mts. between the latter place and the 

 Longitudinal foot of the CorraUto Bar and by another levelling of this 

 Bar where there exists a diiferance in level of 0.40 mts., tin 1 

 general slope of the rivei Uruguay between Concordia and 



section. 



