Guano as compared loith Manure. 343 



the soil, after washing with water and dilute acid, is digested 

 with a small quantity of caustic ammonia. The organic 

 matter rendered soluble is washed out, precipitated by an 

 acid, dried at 250° F., and weighed. This determination it 

 is considered shows at once the present value of the organic 

 portion of the soil — in other words, how much organic mat- 

 ter is so far decomposed, or changed, as to be available for 

 the present crop. The soil after digesting with ammonia and 

 washing, is next treated with a stronger alkali, caustic soda, 

 and the organic matter rendered soluble by this agent is col- 

 lected and determined as before. This estimation, it is con- 

 ceived, shows the amount of organic matter existing in a 

 state not so sufficiently decomposed or changed as to be im- 

 mediately available for the use or nourishment of plants, but 

 in a state preparatory for such use, or nourishment, and which 

 at no distant period will become available. Thus, if we 

 were to represent the organic matter rendered soluble by am- 

 monia as in the state of crenic acid, ready to be dissolved in 

 water, or by the aid of weak alkalies, we might consider the 

 organic matter rendered soluble by soda, as in a state of apc- 

 crenic or humic acid, insoluble in water or weak alkalies. 

 Lastly, it is found that after digesting a soil even with strong 

 alkalies, and after repeated washings with acids and water, a 

 considerable quantity of organic matter will remain fixed, 

 and completely insoluble. This portion of organic matter, 

 generally the largest in a soil, is considered to be in a state 

 allied to charcoal, or more properly lignite, valuable in many 

 respects, as an absorbent of moisture, etc., but taking no ac- 

 tive part in the production and sustenance of the plant. In 

 ordinary soil analyses, the amount of organic matter, in these 

 three conditions is determined as a whole, and without 

 distinction, thus giving the agriculturist no opportunity of 

 judging whether this portion of his soil is in a condition re- 

 sembling a peat bog, or in a state conducive to fertility. 



There is one other subject connected with these analyses, 

 which I consider of the highest importance, and to which I 

 would direct especial attention. Dr. Dana of Lowell, in the 

 course of many years experience, has collected and preserved 



