104 



SCIENTIFIC AGRICULTURE. 



126. What are animal fertilizers ? Are they valuable ? 



127. What is said of the bones and excrements of animals as 

 fertilizers ? 



128. What is the composition of bones ? 



129. How are they sometimes used ? 



130. How are they converted into superphosphate ? 



131. What does sulphuric acid form with calcium ? 



132. Where has a large deposit of bone phosphate been 

 found ? 



133. What other source of superphosphate is mentioned ? 



134. How can a good superphosphate be made by the 

 tanner ? 



135. Give the directions of Dr. Nichols for making it. 



136. What is said of guano and its use in South America ? 



137. What is guano ? 



138. When was it introduced into Europe ? 



139. What does Liebig say of its use ? 



140. When was it brought to the United States ? 



141. Why is the Peruvian guano the best ? 



142. What makes guano so rich a fertilizer ? 



143. Give the composition of guano. 



144. How does Peruvian guano differ from the African ? 



145. Give its properties. 



146. To what is its stimulating effect due ? 



147. What retards the growth of plants ? Is nitrogen sup- 

 plied from the air ? 



148. How does guano act ? Why does it sometimes " run 

 out"? 



149. With what sort of fertilizers is it generally mixed ? 



150. Why should it not be placed next to the seed ? 



151. What is mentioned as a good mixture? How should 

 it be applied ? 



152. Should guano be mixed with lime ? Why not ? 



153. What is said of farm-yard manure ? 



154. Upon what does its value depend ? How can the es- 

 cape of ammonia be determined ? How prevented ? 



