Fixation ot Nitrogkn in Colorado vSoils 215 
At the Dorthern end of this section we have even in surface 
wells only small amounts of nitrates. The first 4 wells given 
show a maximum of 5 p.p.m. of nitric nitrogen which is less 
than may be present in deep wells that are certainly free from 
pollution. Water from a depth of 100 feet is free from this 
form of nitrogen. This well must penetrate the shales for the 
greater part of its depth, and in the adjoining ranch we find a 
surface water at 4 feet carrying less than one part per million. 
^ The water from a little swale through which an irrigating ditch 
runs carries 161.0 p.p.m. of nitric nitrogen. The next one to 
the south is differently situated. Here the surrounding land is 
black on the surface and has ceased to be productive. The soil 
is extremely rich in soluble salts, consisting of chlorids and 
nitrates. The nitrates in these shallow wells are very abundant 
336.0 p.p.m. of nitric nitrogen. The next ground-water south is 
also rich, 309 and 297 p.p.m. of nitric nitrogen. A well 280 
feet deep in an exceedingly bad place yields water of an entirely 
different character, carrying no nitric nitrogen and the salts 
present, while abundant, are sulfates instead of chlorids aurl 
nitrates. The next water obtained south of this was from a 
large well dug to furnish water for a small pumping plant to 
irrigate a piece of land; this was extremely rich, 515 p.p.m. 
This was followed by one with 75.6 p.p.m. and a surface well 
with 131.6 p.p.m. This one is close to a very bad nitre-spot. 
At this place there is also a well 400 feet deep, but in this well- 
water there is no nitric nitrogen. The next well south of this 
is a shallow one on the side of a hill and its water is very bad, 
for which, at this time, we have no explanation. Two or three 
miles south of this and beyond some small lakes, our series of 
samples ends and the water of this southernmost well carries 
only 1.0 p.p.m. of nitric nitrogen. 
WELL-WATERS THREE MILES EAST OF WELLINGTON 
The country south of this is not well opened up and it was 
necessary for us to go one mile east to carry our line of wells 
further south. This statement is made to show the relation be- 
tween the foregoing and succeeding tables. They together 
form a continuous line southward. 
