6S BOARD OF AGRICULTURE. 



the amounts should be accurately ascertained. Now, good, 

 arable, fertile soils will usually contain only perhaps two one- 

 thousandths of their dry weight of the first two of these 

 substances, and about double the quantity of potash. It is 

 evident the fertilizing principles are present only as mere 

 traces; but, if analysis is worth any thing, it must detect 

 and correctly weigh them. The work must be done with 

 the utmost accuracy, as any small fractions of error are of 

 immense importance when the contents of a whole field are 

 taken into account. Difficult and delicate as is the labor, it 

 is quite within the power of the chemist to correctly deter- 

 mine the amounts of these agents existing in soils. If chem- 

 istry had no more difficult service to perform, we would not 

 complain ; but the condition of these elements, or their avail- 

 ability, is a point of great importance, and one almost or 

 quite impossible to confidently settle. The value of a soil for 

 growing crops depends in a great measure upon the condition 

 in which the phosphoric acid, nitrogen, «&c., exist in it ; and, 

 if it cannot be positively shown what that condition is, we do 

 not obtain satisfactory results. When the chemist has esti- 

 mated correctly the amount of the most important fertilizing 

 principles in the covering of an acre of ground nine inches 

 deep, he has acquired but a part of the information needed 

 to enable him to give an opinion of positive value regarding 

 its crop-bearing capabilities. There are also other points of 

 importance connected with the physical condition of soils, 

 which chemistry fails to shed much light upon. There can 

 be no doubt whatever that some soils have the capabilities of 

 appropriating more atmospheric nitrogen than others, and 

 also the decomposition of some of the constituents of soils 

 renders them physically better qualified to promote plant- 

 growths at one time than at another. All these considera- 

 tions should not, however, tend to destroy our confidence in 

 the general aid which chemistry is capable of affording us : 

 they are only calculated to make us cautious, and place a 

 proper estimate upon the help it supplies. 



Of the great light which chemistry has poured upon the 

 structure of plants, the nature of plant-food, and sources 

 of supply, I have not time to speak. This department of 

 the subject has been so recently considered by me in a lec- 

 ture given before a large body of practical husbandmen at 



