Alkalis In Colorado 
17 
any harm. In solutions containing only magnesic sulfate, this salt 
is the most poisonous of all the compounds that we usually speak of 
as alkalis. In the field it seems to be harmless in the quantities that 
are present in our soils. It may be true of other salts as well as of 
magnesic sulfate, that their action on vegetation is modified by the 
presence of other salts, perhaps even by the soil particles, but we must 
not attempt to carry this principle too far; for instance, I do not think 
that we can argue from the manner in which this mixture of alkalis 
effects the action of magnesic sulfate what its effect would be on the 
action of sodic nitrate. In this case 'both parts of these salts are dif¬ 
ferent and the two salts named have no part in common, but I do not 
think *hat this makes any difference in the statement made. I think 
that I can sav of magnesic nitrate, just what I have said of sodic 
nitrate. There is, too, another side to the influence of other salts upon 
the action of a given salt. In the case of magnesic sulfate, the pres¬ 
ence of calcic sulfate and other salts has the effect of lessening - the 
action of the magnesic sulfate. There may be other combinations 
which might make it greater. We know a great many instances in 
which even a small amount of salt may greatly intensify the action 
which may be going on. The reader will recall the statement that the 
presence of calcic sulfate, sodic sulfate, etc., lessens! the action of 
magnesic sulfate. This is mentioned to explain a contradiction be¬ 
tween the results produced in the laboratory and in the field. One- 
experiment is made in glass and the other in the soil. This is a dif¬ 
ference, but the bigger difference is that in the one case only magnesic 
sulfate was present and in the other case a great mass of other salts 
was present to which we attribute the lessening of the bad effects of 
the magnesic sulfate. The reader must not think too little of this 
conclusion because we have chosen the more plausible of two possible 
causes for the difference; further, he must not find fault with the 
explanation, because we have not even attempted to tell him that this 
action is due to this or that individual salt. Our statement represents 
soil conditions as giving different results from our laboratory experi¬ 
ments and all of these salts are in the soil. 
Sodic sulfate is by far the most abundant of our alkalis. Even 
in pure solutions, it is far less poisonous than the magnesium sulfate 
and its poisonous action is lessened by the presence of other salts, 
even calcic carbonate which we might expect to increase its poisonous 
action actually makes it less by four-fifths, so that it is only one-fifth 
as bad in the presence of calcic carbonate as in its absence. Calcic 
carbonate is usually, so far as I know is always, abundant in our soils, 
so that we would expect to find in our field observations that the 
