498 
Journal of Agricultural Research 
Vol. XXIV, No. 6 
their production. But in the summer months when run-off is light and 
decay rapid, the products of decay must accumulate to a very great 
degree. If there is any run-oflF through the tile lines, these products of 
decay will find their way to the tiles along with the drain water. The 
percentage of concentration of the acid in the drain water may be very 
low, but the actual amount passing during a season would be enormous. 
With the drain water also carrying carbonic acid, the complex compounds 
formed with the cement would be immediately carried away, presenting 
a fresh face to the action of the organic acids. 
Though this process is evidently very similar to the leaching of lime 
from surface soil, a little thought will show that they are not exactly 
analogous. The lime in the soil is present in a comparatively inert form. 
It has been demonstrated that the concrete of the tile is chemically active 
even to the very end of the tile. It is possible that the ordinary soil 
is better able to retain the complex lime-organic compounds than 
is the peat. It has been shown that tile near the surface of a well- 
drained peat are not greatly affected. It is possible that the greatest injury 
is done by organic compounds that are produced in quantity only where 
the conditions are suitable. It is possible that these conditions may not 
exist in a mineral soil. This leads us to the statement that the deduc¬ 
tions from this investigation can not be stretched to include the use of 
concrete tile in mineral soils whether acid or alkaline. 
ECONOMIC FACTORS 
Though, under certain conditions, the life of a concrete tile in peat soil 
may be very short, under certain other conditions it may continue a long 
time. In general, it may be said that the average life of concrete tile, as 
they have been made, is about six years. The tile may hold on for a con¬ 
siderable time during which the violent alkalinity is being neutralized, after 
which the final collapse is rapid. In peat soils the collapse of the tile may 
not be as serious as it would be in a mineral soil, nor may the collapse at 
once become apparent. If the drain is not closed by the tramping of 
stock or by farming operations, the underground channel may remain 
open for years, functioning nearly as well as tlie original drain. 
It will probably be said that the quality and density of concrete tile is 
improving rapidly and that the tile at Coon Creek, for instance, were not 
good tile and were condemned before they went into the ground. Even 
though they were not good tile, however, they were no worse than 
many hundreds of miles of tile that have been used. They were shipped 
from the factory while still “green,’' and the first test was made when 
they were only partly cured. That is not the point, however. The point 
is that during the two years in the ground the tile lost in every quality 
that fits them for the work for which they are intended. 
If the average expectation of the life of the tile were 40 or 50 years or 
upward, there would probably be no question as to the advisability of 
using concrete tile, but with an expectation of only 6 or 10 years it does 
not seem that, as now made, their use in peat is sound economics. It 
would seem to be a question whether or not they would pay for the invest¬ 
ment and give a sufficient profit during that time to reimburse the land 
owners for the trouble and business hazard involved. No doubt improve¬ 
ments in the quality of the tile which are now being generally made will 
greatly increase the life of the tile, but those improvements are with few 
