1917] Lipman-Gericke : Smelter Wastes and Barley Growth 497 



would be possible in the vicinity of smelters. (3) To ascertain 

 whether the same substances would be a menace to lands more 

 remote from smelters if carried down to them in solution in 

 irrigation water of streams polluted by solid smelter wastes. 

 (4) To ascertain whether the compounds named may exercise a 

 stmulating effect on plants grown in soil as a medium and, if 

 so, whether the effect noted is ephemeral or permanent in one 

 way or another. (5) To ascertain whether potassium aluminum 

 sulfate can have any value as a source of potash or as a plant 

 stimulant. 



METHODS OF THE EXPERIMENTS 



The experiments were carried out in the greenhouse, the 

 successive crops being grown at different seasons of the year 

 so as to allow a study of the effects of a variety of climatic con- 

 ditions. The plants were not artificially shaded during the 

 period of growth. The soil used in most of the experiments was 

 a clay adobe containing a very good supply of organic matter to 

 start with, and was made up by adding barnyard manure to our 

 hillside clay adobe soil. The other soils employed in a number 

 of the experiments which served as checks on the heavier soils 

 were a blow sand from Oakley, California, and the clay adobe 

 soil above named unmixed with manure. Evidence is thus 

 obtained of the effects on barley of at least one of the salts 

 mentioned, in four types of soils, since a humus sand was, as 

 explained above, employed in the preliminary experiments. The 

 chemical analysis by the Hilgard strong acid digestion method 

 of the humus clay adobe, of the blow sand, and of the clay adobe 

 yielded the results shown in table 1 (p. 498). 



The containers for the soils just described were ordinary 

 earthenware pots nine inches in diameter at the top. These pots 

 were paraffined to preclude the possibility of the absorption of 

 salts by the porous walls. From ten to twelve pounds of soil 

 were used per pot, depending upon the kind of soil employed. 

 The salts were applied in solution in all cases except in that of 

 the lead sulfate, which, owing to its insolubility, was mixed, in 

 the form of powder, with the soil. The mixing was done as 



