210 INTRODUCTION TO GENERAL SCIENCE 



Weigh all the chimneys, with their contents, taking care to 

 number them. Weigh every twenty-four hours, and make a 

 table of your results. State your conclusions. 



150. IRRIGATION AND UNDERDRAINAGE 



The artificial watering of land is called irrigation. Irri- 

 gation is of the utmost importance, since about two -fifths 

 of the area of the United States is too dry for farming. Up 

 to the present time, a little over ten million acres are irri- 

 gated, which is a mere nothing compared with the dry area. 

 Proper irrigation, that is, where there are several thousands of 

 acres to be irrigated, must be a national enterprise, since it is 

 impossible for communities, or even groups of men, to com- 

 bine in order that they may put into operation any large 

 irrigation system. Irrigation should be used where the soil 

 needs more water, whether in a dry or humid climate. Al- 

 though the cost of irrigation is considerable, yet the results 

 pay, for it will give a large pecuniary gain. In this connec- 

 tion it might be well to understand that the actual outlay of 

 money for improvements must not be thought of as expense, 

 if the returns justify the expenditure. The same is true in the 

 fertilization of the soil. If the addition of several hundred 

 dollars' worth of fertilizer produces enough extra crop to pay 

 for the fertilizer and give a fair profit, the cost of the ferti- 

 lizer should not be considered at all. For the practical con- 

 sideration of irrigation in field and garden, Farmers' Bulletin 

 No. 138, written by Professor E. J. Wickson, leaves little 

 unsaid. 



Too much water is nearly as bad for plants as too little 

 water; they will not grow if the roots remain in water, since 

 the necessary air is thereby excluded from them. Under- 



