Note 65 — Chapter III · THE POSITION OF NITROGEN IN AGRICULTURE.
Reading edition
Although ammonia is more abundant than nitrates and nitrites, it only amounts to a few parts per million of air. According to Müntz, the air at great heights contains more ammonia than in its lower strata. The opposite, however, is the case with regard to nitrates, which are only found in air near the surface of the earth. See p. 49.