QUESTIONS SUGGESTED. 



c Independently of their effect upon the quantity, what in- 

 fluence do they respectively exercise on the quality of the crop? 

 Is the proportion of nitrogen in the grain of wheat, or in the 

 bulb of the turnip, increased or decreased by the use of these 

 substances, or by uric acid and the nitrate of urea ? Is the in- 

 crease or decrease equal to, or does it bear any relation to that 

 caused by the salts of ammonia, or by the nitrates ? 



d Does the proportion of carbon with which the nitrogen is 

 associated in urea, uric acid, or oil-cakes, bear any relation to 

 the differences in their effects as compared with those of am- 

 monia or its salts ? 



A careful perusal of the introductory sections of the present 

 chapter will cause the thinking field-experimenter and chemical 

 analyst to ask himself many other such questions as these. 





