1906.] GEOLOGY IN RELATION TO WATER SUPPLY. 293 



enough to be noticed in atlases carry more water to the sea 

 during certain seasons of the year than great rivers hke the 

 Rio Grande and the Colorado River of Texas. A chart show- 

 ing the discharge of the Housatonic River at Gaylordsville 

 shows considerable variation, but there is enough water in the 

 stream at all times to form a good river. The Rio Grande, 

 on the other hand, varies between great abundance of water 

 and stages when the valley of this large stream is dry. 



There is no lack of water in Connecticut rivers, and as a 

 supply for household purposes the river waters of the State 

 are by nature entirely satisfactory. Increase in population 

 and the development of manufactures have made the river 

 waters of little value, but their loss of value is due to artificial 

 conditions and does not depend upon geological structure 

 of the State. 



Lakes of Connecticut. One of the most marked features 

 of the Connecticut landscape in the presence of lakes, ponds, 

 and swamps. They owe their existence almost entirely to the 

 fact that Connecticut has been overridden by a continental ice 

 sheet. The land has been entirely remodeled, certain valleys 

 have been filled, others scooped out. Materials of dififerent 

 characters have been widely and unevenly spread throughout 

 the State, and the region, which perhaps before the Glaciil 

 age was thoroughly well drained, has now many places where 

 the water remains for a considerable time before it is finally 

 carried into the sea. 



The great number of these lakes is manifest by the fact 

 that on the topographic atlas of Connecticut there are mapped 

 1,026 lakes and 420 swamps. Lakes owe their permanency 

 to the fact that evaporation is not so great as the supply of 

 water, and wherever a lake occurs it is an indication that the 

 water table or level of ground water stands permanently up to 

 that height. In regions of slight rainfall the mineral particles 

 in the water are concentrated, the lake becomes salt, and may 

 entirely disappear by continued evaporation, leaving nothing 

 but a plain of muds and sands carrying a high per cent of 

 salts of different kinds. The lakes of Connecticut, however, 

 are not in danger of extinction in this way. Their outlets 

 may be cut down and the water thus drained, and they may be 

 filled with sediment brought in by muddy tributaries, but 

 most of them are doomed to extinction by the action of plant 



