540 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



vegetation in a highly diluted state, but injurious when they 

 occur in land too abundantly? 



" 3. Whether barrenness is caused by the absence or de- 

 ficiency of lime, phosphoric acid, or other important elements 

 of plant-food ? 



"4. Whether clays are absolutely barren and not likely to 

 be materially improved by cultivation ; or whether they con- 

 tain the necessary elements of fertility in an unavailable state, 

 and are capable of being rendered fertile by subsoiling, deep 

 cultivation, steam-ploughing, and similar mechanical means? 



"5. Whether or not clays are usefully burned, and used in 

 that state as manure? 



"6. Whether or not land will be improved by liming? 



"7. Whether it is better to apply lime or marl or clay on 

 a particular soil? 



" 8. Whether special manures, such as superphosphate or 

 ammoniacal salts, can be used (of course discreetly) without 

 permanently injuring the land ; or whether the farmer should 

 rather depend upon the liberal application of farm-yard ma- 

 nure that he may restore to the land all the elements of fer- 

 tility removed in the crops? 



" 9. What kinds of artificial manures are best suited to soils 

 of various composition ?" 



We may add, with due respect to Dr. Voelcker's great 

 knowledge of the subject, that his estimate of the value of 

 soil-analysis is fully as high as agricultural chemists gener- 

 ally would put it. It is to be noticed, also, that the above 

 questions are, in Dr. Voelcker's opinion, "frequently,'' but 

 not always, answered by soil-analysis. 



NITRIFICATION. 



"The formation of nitrates in the soil, under favorable con- 

 ditions as to moisture, temperature, and aeration, is a reac- 

 tion well known and much studied. It is a process of great 

 technical importance, being the only natural source of salt- 

 petre. It is also of the highest importance to the scientific 

 agriculturist, nitrates being invaluable as plant -food, and 

 their loss by drainage one of the most serious difficulties 

 with which the farmer has to contend."' The nitric acid in 

 the soil comes from nitrogenous vegetable or animal matter 



