90 



PHYSIOGRAPHY 



ancient civilizations. In America, valleys have been sought out 

 for habitation from the earliest times. In Virginia and Maryland, 

 early settlements were made in the valleys of the James and the 

 Potomac; and in Pennsylvania, in the valleys of the Delaware, the 

 Schuylkill, and the Susquehanna. In New York, the principal 

 settlements were long confined to the valleys of the Hudson and the 

 Mohawk, and when the settlements in Massachusetts began to 

 spread beyond the coast, they occupied the valley of the Connecticut. 

 Alluvial plains are well situated for irrigation. Fig. 92 shows 

 an irrigation canal into which water is to be turned at the point 

 where the canal leads off from the stream. Fig. 93 shows a canal 



Fig. 93. An irrigating canal filled with water. Salt River Valley, Ariz. 



filled with water, along which luxuriant vegetation has sprung up. 

 Trees along the canals serve a useful purpose, for by shading the 

 canal they diminish the evaporation. Fig. 94 shows a field prepared 

 for irrigation. Water is turned from the canals into the small 

 ditches of the field, as needed. 



Great progress has already been made in the use of the arid lands 

 in the western part of the United States for farming purposes. 



