632 



SCIENCE 



[N". S. Vol. XLII. No. 1088 



authoritative information of this type seem- 

 ingly has met with success, and other guide- 

 books in this series will follow in other years. 

 More than that, however, the reflex influence 

 of this innovation is already felt, and the evi- 

 dent appreciation by the general public of this 

 tjrpe of popular description is encouraging the 

 Survey writers. The educational responsibil- 

 ity of this federal service is being more fully 

 realized, and we intend to give much more at- 

 tention both to the simplification of the lan- 

 guage of the professional publications and to 

 the issue of reports that shall be popularly 

 descriptive and instructive without loss of 

 exactness. Even if plain language is used our 

 reports should be no less efficient vehicles for 

 professional discussion or for the announce- 

 ment of geologic discoveries. 



For thirty-six years the United States Geo- 

 logical Survey has reached an ever widening 

 circle of readers, and even in the early years 

 of the Survey's life King and Emmons and 

 Gilbert gave to the West the results of their 

 work in strong and forceful English. Tet 

 with the growth of the organization and the 

 development of the science the tendency to- 

 ward highly specialized writing has been too 

 marked and the present plea for plain writing 

 has become necessary. The government scien- 

 tist has at least two obligations : first, that of 

 making his investigations more and more exact 

 in method and direct in result ; second, that of 

 making his product, the written report, such 

 as to meet the needs of not only his professional 

 associates but also the general public. It is 

 our ambition that the reports of the United 

 States Geological Survey shall be written in 

 the language of the people. 



George Otis Smith 



V. S. Geological Survey 



SOIL FERTILITY 

 As long as a soil continues to produce 

 moderate crops, the question of its fertility 

 arouses no concern, but when the yield falls 

 below normal the reason for this decrease is 

 immediately sought. Until a short time ago 

 it was believed that this difficulty admitted of 

 an easy solution, but when the farmer saw his 



crops decreasing and sought the cause, the type 

 of answer which he received depended on 

 whether he consulted a soil physicist, a soil 

 chemist, or a soil bacteriologist. In any case 

 it was generally conceded that the supply of 

 " plant food " had been exhausted and the only 

 question remaining was how to replenish it. 



The soil physicist saw in this undesirable 

 condition, from his standpoint, a violation of 

 the maintenance of one of the following re- 

 quirements for the soil under examination. 

 First, the proper temperature had not been 

 established in the soil to admit of the rapid 

 growth of crops; second, the proper ventila- 

 tion of the soil had been interfered with, either 

 by a change in the porosity of the soil due to 

 physical or chemical changes, or to the deposi- 

 tion and retention of the by-products of the 

 crops; or third, the plant did not receive suffi- 

 cient moisture and this was due to the non- 

 operation of one of the following agencies, 

 osmosis, surface-tension or transpiration. The 

 importance of this third point is very apparent 

 when we remember that all plant food taken 

 from the soil must be in solution. 



The following quotation from Johnson's 

 " Agricultural Chemistry " illustrates the 

 standpoint of the chemist of a few years ago in 

 regard to soil problems. 



The art of culture is almost entirely a chemical 

 art, since nearly all its processes are to be ex- 

 plained only on chemical principles. If you add 

 lime or gypsum to your land, you introduce new 

 chemical agents. If you irrigate your meadows, 

 you must demand a reason from the chemist for 

 the abundant growth of grass which follows. 



The extension of such ideas as are contained 

 in the above quotations led to the belief that 

 there is a certain definite relation between 

 the productiveness of the soil and its content 

 of nitrogen, potash, phosphoric acid or other 

 chemical constituent, and many persons be- 

 lieve at the present time that from a chemical 

 analysis of a soil the analyst can tell just the 

 kind and amount of fertilizer to be added in 

 order to increase its productiveness. 



With the introduction of more exact methods 

 in bacteriology and the perfecting of bacteri- 

 ological technique, all of which has taken place 



