56 MODERN STRAWBERRY GROWING 
4. Tile costs about $90 per acre, where 
they are laid in rows five feet apart, and in 
good digging not less than $20 per acre is 
required to lay the same; therefore too ex- 
pensive. 
5. Rains fall from above and soak into the 
soil, drawing air down into the soil, causing 
the soil to be aerated. Sub-irrigation lessens 
this process as the water does not draw so 
much air into the soil. 
Overhead system.—To date, this may be 
called the best system as it has many of the 
advantages of the former methods and more 
advantages of its own. It is very economi- 
cal of labour and water, resulting in great 
savings where these two items are costly. 
The Skinner system is typical of this 
method, and was first used by the inventor 
in the spring of 1897, and has been in con- 
tinuous operation since. It was first given 
to the public in 1904, 
The system consists of parallel lines of pipe, 
in which are inserted especially devised 
nozzles, located in the pipe at distances ap- 
proximately four feet apart. The nozzle lines 
are from forty to sixty feet apart, depending 
upon the local conditions. The water is 
