SOILS AND MANURES. 363 



attention has been attracted to this subject, and plans have 

 been broached for avoiding this enormous waste. 



QUESTIONS. 



486. State the analogy between the stomach of an animal and the root 

 of a plant. What is said of the difference in the proportion of nutritious 

 substance ? 487. State the analogy in regard to loosening the soil. What 

 influence has clay upon soil ? What effect has the cold of winter upon it ? 

 What is said of earth-worms ? 488. What of water in the soil ? 489. 

 From what source comes the principal part of the soil ? In what two ways 

 can you see what its chief source is ? 490. What is the second source of 

 the soil ? What name is given to the product from this source ? What 

 is said of its chemical character ? What are the products of its decompo- 

 sition ? What mechanical effect does this decomposition produce ? What 

 other effect is mentioned ? 491. State in full how soil was originally made. 

 What is weathering ? 492. Describe the process of making soil as seen in 

 volcanic countries. 493. How are peculiarities in soil produced? What 

 are the three chief mineral ingredients in soil ? What are some of the dif- 

 ferent soils made by different proportions of these ingredients ? What is 

 said of the mechanical differences of soils ? 494. What is said of the rota- 

 tion of crops ? 495. Follow out the analogy between stomachs and roots 

 in regard to amount of food. W T hat is the object of manures ? What cir- 

 cumstances should govern the selection of the kind of manure ? What is 

 said of the term manure, and of the modes in which manures act ? 496. 

 Illustrate the truth that a knowledge of chemistry is necessary to a suita- 

 ble application of manures. What opportunities often offer for ascertain- 

 ing the chemical character of subsoils ? What is said of hydrochloric acid 

 as a test of the character of soils ? 497. What of the management of vola- 

 tile substances in manures ? 498. What of animal manures ? 499. What 

 is guano ? What is said of its abundance ? What are the chemical in- 

 gredients that give it its value ? Why is the guano of Peru better than 

 that of Africa and Patagonia ? Why are wood-ashes a good addition to 

 guano when used ? 500. State the test of guano by combustion. State 

 the lime test. The vinegar test. The test with hot water. 501. What 

 are the ammoniacal salts present in various manures? What is said of 

 gas-liquor? 502. What is the composition of bone? What is said of the 

 fertilizing powers of the ingredients ? What of their use in regard to dif- 

 ferent crops ? What of the value of bone-dust ? What of its degree of 



