[421] SCIENTIFIC MANUAL. 135 



length of 12 or 13 inch tile is considered, and that these 

 joints cannot be made without cement (which is never 

 used) so close as to exclude water, the question contains 

 no difficulty. 



It is estimated that, in the case of one inch pipe, " the 

 capacity of admission at the joints more than equals the 

 caliber of the pipe every two rods," no fear need, there- 

 fore, be entertained by those using tile pipes for drains, 

 in reference to the water entering the pipe. 



Those wishing to investigate this subject more in detail 

 should read " Land Drainage," by Klippart, which has 

 been freely consulted in the preparation of this chapter. 



CHAPTER XI. 



IRRIGATION. 



In the northern half of Georgia, where there is ample 

 fall in the water courses for the purposes of irrigation, the 

 topography of the country is too irregular to admit of a 

 general system of irrigation. 



In the southern half there is generally insufficient fall in 

 the streams. 



Apait from these considerations, however, the necessity 

 for irrigation will never be sufficiently felt in Georgia to- in- 

 duce large expenditures of money for that purpose. 



By reference to the records given in the '' Hand Book of 

 Georgia," the average annual rainfall for five years, from 

 1871 to 1875, inclusive, at West End, near Atlanta, is 

 found to be 53.32 inches, and that at Macon 54.88 inches. 



" From observations through a long series of years, by the 

 Smithsonian Institute, it has been found that the average 

 annual amount of rainfall in the several sections of the 

 State is approximately as follows: North. Georgia, 50 in- 

 ches; Middle and East Georgia, the northern part of south- 

 west Georgia, and southeast Georgia, 55 inches; the mid- 



