RESERVOIRS AND PONDS. 85 



region, and countless numbers of them scattered here 

 and there over the lands would greatly increase the 

 humidity, and bring about a marked meteorological 

 change for the better. In Western Kansas, for in- 

 stance, a small frac5lion of the precipitation during the 

 year would make a lake one-fourth of a mile square 

 and five feet deep for every secflion of land. This 

 could be utilized easily for irrigation. 



A grand system of reservoirs in arid America 

 would greatly reduce the dangers of floods and render 

 immunity from the horrors of deluge that every year 

 come to the settlers along the lower Mississippi. The 

 ancients understood this principle, for, in order to 

 remedy the inconvenience of the torrential period, 

 when the country was flooded, and of the subsequent 

 drouth for five months, the Romans covered their 

 African provinces with a network of hydraulic struc- 

 tures. From the summit of the mountains to the sea 

 all the rains that fell were seized upon, led here and 

 there in channels, and distributed over the fields. In 

 the smallest mountain ravines stone dams were built to 

 retain water. In the valleys they arrested its progress 

 down-stream. By this means the Romans prevented 

 great floods descending the mountains at times of 

 heavy rains, and retained a larger part of the precipi- 

 tation in the higher reservoirs until such time as the 

 water thus preserved was needed. At the entrance to 

 each large valley was a system of works which assured 

 not only the watering of that immediate region but 

 conducfled flowing streams through many channels, so 

 that the surrounding earth could absorb what was re- 

 quired. At the entrance of each large stream on a 



