780 



SCIENCE 



[N. S. Vol. XXXIII. No. 855 



utmost importance, and yet one of the great- 

 est difficulties encountered, is the mastery of 

 the proper method of disintegration, especially 

 of the insoluble substances and those which are 

 likely to lose part of their content by volatili- 

 zation. If a proper solution of the unknown 

 is obtained, the analysis is comparatively easy, 

 whereas, if not obtained, incorrect results are 

 sure to follow. Alloys and metallurgical prod- 

 ucts containing relatively small amounts of 

 some one substance also require special atten- 

 tion. 



Objections have been raised to the use of 

 technical products for unknowns, claiming 

 that they do not give the proper amount of 

 training. This is apt to be true where un- 

 knowns of a commercial nature are taken just 

 as they come to hand without special effort on 

 the part of the instructor. It is certainly not 

 the case if care is taken in obtaining what is 

 necessary to suit the problem in question, for 

 there are certainly sufficient varieties of com- 

 mercial products to cover the field. Aside 

 from giving the students a training not to be 

 had in the use of laboratory prepared un- 

 knowns, his interest is much more easily 

 aroused and held when he can see something 

 " practical " in what he is doing. 



I have found that where lectures are com- 

 bined not alone with class-room quizzing but 

 as well with this demonstration method the 

 student is made to think and gets a grasp on 

 the subject well worth the time spent in its 

 acquisition. 



Eaymond C. Benner 



Univeesitt op Arizona, 

 Tucson, Ariz. 



EUMUS IN DEY-LAND FABMING 

 It has been the consensus of agricultural 

 opinion and experience, both in this country 

 and in Europe, that the production of wheat 

 on the same land year after year results in 

 steadily decreasing yields. Chemical investi- 

 gations in several instances have shown this 

 decrease in yield to be accompanied by a cor- 

 related decrease in the supply of humus and 

 of nitrogen in the soil. Under the title of 

 " The Nitrogen and Humus Problem in Dry- 



Land Farming," Mr. Robert Stewart, chemist 

 of the Utah State Experiment Station, has re- 

 cently published the results of some investi- 

 gations with special reference to the effect of 

 continued wheat growing on the non-irrigated 

 lands of the Cache Valley in Utah.' 



Mr. Stewart's investigations in the Cache 

 Valley indicate that the continuous produc- 

 tion of wheat in that section has not resulted 

 in a reduction of either the humus or the 

 nitrogen supply of the soil, at least during the 

 thirty years or more that wheat has been so 

 grown there. He finds, indeed, that in some- 

 thing over twenty cases where comparisons 

 were possible between virgin soil and soil that 

 had been cropped to wheat for several years 

 there has been a slight increase, both in the 

 total nitrogen and the humus in the surface 

 foot. In the second foot of soil on these two 

 sets of fields he finds a decrease of the total 

 nitrogen on the cropped land, but a marked 

 increase in the humus. His summary of re- 

 sults shows that on the wheat land there has 

 been a 10 per cent, increase in the humus 

 supply of the surface foot and a 25 per cent, 

 increase in the second foot. 



Mr. Stewart wisely avoids any generaliza- 

 tions upon the limited data he presents in this 

 publication. But it is unfortunate that he 

 does not give more consideration to the agri- 

 cultural conditions and farming methods that 

 prevail in the region of which he writes. Un- 

 less the reader of Mr. Stewart's bulletin is 

 familiar with conditions in the Cache Valley, 

 the results presented are likely to seem either 

 pointless or irreconcilable with the results of 

 similar investigations elsewhere. To one 

 who knows those conditions, the brief state- 

 ment that " Some of the farms of this dis- 

 trict have been under cultivation for forty-five 

 years, and apparently yield as good crops as 

 they ever did " may seem to be a good and 

 sufficient epitome of the situation; but if one 

 does not know the region, this sentence hardly 

 seems adequate. 



It is true that accurate data as to the farm 

 yields for past years are difficult to obtain and 



^ Utah Agricultural College Experiment Station 

 Bulletin, No. 109, August, 1910. 



