FERTILIZERS : — AGRICULTURAL, INTELLECTUAL, ETC. 169 



the mind, of just what sort of help Nature needs in that special 

 field, and also with direct reference to the crop to be raised. We 

 are to call in the skill of the practical chemist on the one hand, 

 and in the other field the skill of the man who can analyze the 

 mental qualities and tendencies, — who can see what mental chemi- 

 cals, so to speak, there is a deficienc}' of in any given mind, 

 and which are to be supplied if the mind is to yield its best results. 



The recognition of the second demand of this law is what has 

 brought horticulture, or agriculture at large, up from a compara- 

 tively low level to the high place it now holds, where the learned 

 man of science is made the paid servant of the farmer and the 

 gardener, — as much so as the man who holds the plough or drives 

 the team. Likewise (to keep up the parallel) the recognition of 

 the above-named second demand of this same law is what is effect- 

 ing the present beneficent revolution of common school and univer- 

 sity education, culminating in the elective sjstem now being 

 introduced into so many of our colleges, instead of that Procrus- 

 tean bed on which formerl}' we all had to be stretched. 



Now let us strike our plough into the soil. The first demand 

 under that law was that we secure those aids or appliances which 

 will develop into productive agents the power latent in the field. 

 Under this head, I name air and water as the two great assistants 

 first of all to be looked after and secured by the horticulturist. 

 Their value, — nay, their indispensable agency, — is too often neg- 

 lected in the eager demand for commercial fertilizers which will 

 supply the largest percentage of nitrogen, phosphoric acid, and 

 potash. There is a tendency to trust to these last-named helps so 

 entirely as to overlook the necessity of securing the eflTective help 

 of those two natural agents. In speaking thus of the air and water 

 I do not refer to irrigation, but to the provision which should be 

 made (and so seldom is made on a liberal scale) for having them 

 permeate the soil freely and perform their own most individual 

 and peculiar service. 



And exactly what is this service? It is by the chemical action 

 upon the native material in the soil to convert into " plant food " 

 what else were dead matter. An immense amount of such matter 

 lies unused and utterly unusable for lack of the action upon it of 

 air and water to put it into such form that plants can assimilate it. 



The fact of the existence of this vast supply of the raw mate- 

 rial in many soils which seem utterly lacking in fertilitj' was ree- 



