Gravel. 



EASY EXTRACTION 



OF SAND BY THE 



AID OF SUCTION 



DREDGERS. 



Downs. 



Negro and Fray Bentos mud is found over a great extension 

 especially in the shallow parts which the navigators carac- 

 teristically call «E1 Barrial». The bed of the creeks and 

 smaller channels as far as Conception del Uruguay is also 

 mud. 



In the bar « Altos y Bajos» the suction dredger showed 

 the existance of gravel at a depth of six meters under the 

 zero of the gauge and the columns of the jetty of Concep- 

 cion are placed in the same material which is situated under 

 a layer of sand about 2 meters thick. 



Going up stream the gravel appears more frequently and 

 forms between Nueva Escocia and Concordia nearly exclu- 

 sively the river bed. 



It may be stated that, except in the stone bars of «Corra 

 lito and Hervidero», the Middle Uruguay does not bring- 

 down gravel during the great flows of water and that the 

 gravel which is found in the river bed is not brought clown 

 from great distances but from both banks where layers of 

 this matter are found at the surface of the ground or under 

 a thin layer (cap) of humus. 



The shallow parts formed by gravel of a diameter from 

 3 to 5 centimeters are specially found in the part of the river 

 where the underground on account of its hardness has not 

 been excavated and acts as a weir. This gravel forms a 

 conglomerate were great velocities of current are observed. 



Where the conglomeration does not exist, the sand, the 

 weight of which is about 1500 kg. per cub. met., is easily 

 raised by the suction dredger N° 11 C, whose speed of water 

 in the suction pipe is only 3,50 meters per second. The 

 specific weight of the sand causes it to deposit quickly in 

 the hold of the barge and only a very small quantity flows 

 over board back to the river. 



At certain places the sand forms downs, as for instance 

 on the Oriental coast at Nueva Palmira on the North and 

 South side of the Arroyo Negro and on the Argentina Coast 

 north of the jetty of Concepcion del Uruguay, on the island 

 «Marineros» opposite Paysandu and at the canehas of 

 Pepeaji and San Jose\ 



The sand banks in the river contain a greal amount of 

 quartz which does not allow any vegetation, they are easily 



