54 AGRONOMY 



7. Select two thermometers graduated alike and place them so that 

 their bulbs only will be exposed to the sun. Cover one bulb with a 

 white cloth and the other with a black one. Which thermometer now 

 measures higher ? How much ? Explain. 



8. Take the two thermometers and cover both bulbs with the same 

 kind of cloth. Wet one cloth and leave the other dry. What difference 

 do you now find in the way they register ? Explain. Does fanning them 

 have any effect upon the temperature registered ? 



9. Change 40 C. to Fahrenheit ; 60; 85. 



10. Change 68 F. to centigrade; 95; 41. 



11. From the nearest weather observer find the average rainfall by 

 months for the past five years. Plot the curve for the year as in 

 Fig. 26, p. 51. The numbers at the left indicate the amount of rain- 

 fall in inches. What is. the average annual rainfall of your region ? 



12. Plot the rainfall curve for the present year or for the preceding 

 one. Is the rainfall well distributed through the growing season? 



13. Make a similar curve for the average temperature by months 

 for the past five years. 



14. In a rainfall of half an inch how many cubic inches fall on an 

 acre of ground ? how many gallons ? how many barrels ? How many 

 gallons fall on the school garden ? on your own plot in it ? 



15. What is the total amount of water that fell on the school gar- 

 den last month ? 



16. If an acre of ground is half pore space, how many gallons of 

 water will be contained in the upper 7 in. when the soil is saturated ? 



17. From wells in the vicinity ascertain how far below the surface 

 the water table lies. 



18. Visit a marsh, hillside, or ledge of rocks, and decide what causes 

 the water table to come to the surface here. 



19. Visit lands that have been tile drained. Are there any other 

 lands in the vicinity that would" be benefited by the same treatment ? 

 Are there any lands that open ditches would serve better? any land 

 where irrigation could be practiced to advantage ? 



References 



Farmers' Bulletins 



46. Irrigation in Humid Climates. 

 138. Irrigation in Field and Garden. 

 187. Drainage of Farm Lands. 

 263. Practical Information in Irrigation. 

 371. Drainage of Irrigated Lands. 



