Septembeb 28, 1906.] 



SCIENCE. 



389 



soil, and without humus, which gives life 

 and activity are practically useless as a 

 medium for plant growth.' This state- 

 ment is an attractive one, and may be in 

 a broad sense correct, but, notwithstand- 

 ing all of the investigations that have been 

 made, I am of the opinion that much has 

 yet to be learned as to the function of 

 humus and the influence it exerts in the 

 maintaining and improving of the fertility 

 of our soils. We are unable from our pres- 

 ent knowledge to state whether the effect is 

 physical, chemical or biological, or whether 

 it is a combined effect of each, or whether 

 it is absolutely essential that the organic 

 matter be present in large amounts, in 

 order that the best results may be obtained. 

 It is a problem well worthy of the atten- 

 tion of our agricultural chemists, and one 

 which must be solved, if we are to give 

 safe advice as to the cultivation of our 

 soils. 



Still another problem, which is agitating 

 the minds of many far-seeing investigators, 

 is the question of the supplies of artificial 

 plant-food, aside from that involved in the 

 question of nitrogen. As already pointed 

 out, it has been clearly demonstrated that 

 so far as the mineral elements are con- 

 cerned, there is sufficient in the soils of 

 this country to supply the needs of maxi- 

 mum crops for centuries, but this state- 

 ment must be modified, so as to read 'sufii- 

 eient to supply the needs of general crops, 

 cereals and grasses, or any other crop which 

 in its cultivation is allowed to develop un- 

 der natural conditions,' but it does not 

 apply to that class of crops, the need of 

 which is increasing rapidly, that can not 

 be grown to perfection in such quantities 

 as to meet the demands of a modern civil- 

 ization, without the stimulating effect of 

 immediately available plant-food. I now 

 refer to the large number of vegetable 

 crops, fruits, berries, etc., which must be 



produced under semi-artificial conditions, 

 in order that they may possess those char- 

 acteristics of quality, and be provided at 

 such times as the present demands require. 

 There will, therefore, be a constantly in- 

 creasing demand for plant-food, which can 

 not be supplied by natural means, includ- 

 ing the use of home-made manures. 



The nitrogen question, as already pointed 

 out, has received the attention of eminent 

 investigators, and the problem has been 

 solved in so far as the actual obtaining of 

 free nitrogen from atmospheric sources, 

 both by means of special classes of crops 

 and by chemical combination. How soon 

 the latter may be a practical source is still 

 a question, but the progress thus far made 

 indicates that the solution will be reached 

 in the near future. There is, however, 

 still a broad field for study, as to the source 

 of supply of phosphates and of potash 

 salts. "We have in this country, and in 

 Canada, enormous deposits of phosphate 

 rock, already exploited; others will un- 

 doubtedly be found, so that the question 

 is not one that requires such immediate at- 

 tention. Nevertheless, with the great de- 

 mands which are likely to be made, it is 

 one well worthy of the study of our chem- 

 ists. In the case of potash, we have no 

 source of supply, at present, other than 

 the Stassfurt mines of Germany, and the 

 time must come, sooner or later, when 

 these will not be able to meet the demand. 

 Whether the potash stored in our granite 

 hills are to supply these demands, or 

 whether unknown deposits exist in our 

 country, are questions that must occupy 

 the minds of our agricultural chemists, 

 and are problems which are of fundamen- 

 tal importance, because they have to do, 

 not only with the production of crops, but 

 with the future progress of humanity. 



Still another question, or problem, which 

 it seems to me the chemist should solve, 



