SCIENTIFIC AND PRACTICAL AGRICULTURE. 239 



blacksmith's anvil ? 54. For what are these good ? 54. How 

 are they to be applied ? 54. 



What gives to some soils their red color? 54. To others their 

 sickly yellow? 54. How can these last be cured? 54. 



What can you say of the peroxide, or black oxide of mtnga- 

 nese? 55. 



How is potash composed? 56. What is said of its caustic 

 power? 56. What has to be combined with potassium, to make 

 it potash? 56. What with potash to make it carbonate of 

 potash ? 56. What with that to make it bicarbonate ? 56. In 

 v/hat form is it applied to land ? 56. In what form does potash 

 exist in ashes ? 56. How much carbonate of potash is there in 

 common wood ashes ? 56. How much soda ? 56. How much 

 lime? 56. 



Will you trace sodium through its combinations up to carbo- 

 nate of soda ? 57. To sulphate of soda ? 57. What is soda-ash ? 57. 



Wliat is lime ? 58. What is water-slacked lime ? How much 

 water does it take in ? 58. What is air-slacked lime ? 58. Trace 

 the metal calcium through its combinations ? 58. What does it 

 form if combined with carbonic acid? 58. With sulphuric acid? 

 58. With silicic acid ? 58. With muriatic acid ? 58. What are 

 those substances called which consolidate water in themselves 

 and yet appear to be dry, as slacked lime ? 58. 



Magnesia is obtained from sea-water and from a species of 

 magnesian lime-stone, called dollomite ; it exists in this lime-stone 

 and in sea- water, as carbonate of magnesia; if the carbonic acid 

 is driven off. what does it become ? 59. 



How is alumina composed ? 60. Of what is it the basis ? 60. ^ 

 What is pure clay? 60. 



What is chloride of sodium? 61. Why may common salt be 

 beneficial to corn, potatoes, and turnips? 61. 



How many sulphurets of iron are there? 62. What' is the 

 bisulphuret sometimes called ? 62. ,Why? 62. 



How is sulphuretted hydrogen composed ? 63. It is a light, 

 evanescent gas; where may it often be detected by its smell? 63, 

 What is said of its influence on health ? 63. On the growth of 

 plants? 63. 



What is the name of that gas which often rises in bubbles in 

 stagnant water ? 64. Of that which is used for purposes of light- 

 ing? 64. What experiment is mentioned in 64? 



What is the composition of ammonia ? 65. How is its odor 

 recognized ? 65. Where is it generated ? 65. If left to its own 

 course, what does it become? 65. Where does it go? 65. How 

 is it brought back to the earth ? 65. Can its escape be arrested ? 65. 



GEOLOGY^ 



What is the form of the earth ? 66. What inference from this 



