240 CATECHISM OF 



with regard to the state in which it once was ? 66. What is its 

 average weight? 66. 



How many square miles on the earth's surface? 67. How 

 many square miles of land ? 67. How many of water ? 67. What 

 is the height of the highest land ? 67. The depth of the deepest 

 water? 67. The probable average height of land? 67. The 

 average depth of water ? 67. 



(If we suppose the population of the globe to be 1000 million, 

 we have 32 acres to each person ; if the population should double 

 once in 25 years, there would be, in 200 years, 4 persons to each 

 acre.) 



What is said of the crust of the earth ? 68. With what is it 

 covered ? 68. What is the weight of the atmosphere to the square 

 inch of the earth's surface ? 68. To the square foot ? 68. Of 

 the whole atmosphere ? 68. 



What is the difference between stratified and unstratified 

 rocks ? 69. How must the unstratified rocks have been formed ? 

 69. What are they called ? 69. 



How did the stratified rocks receive their present form ? 70. 

 What are they called? 70. What else are they called, and why? 70. 



Which rocks are the older? 71. Which the newer? 71. Give 

 the illustration? 71. 



Could the igneous and the aqueous rocks have been formed at 

 the same time ? 72. Why not? 72. 



What classes of rocks do we find above the igneous ? 73. Give 

 some account of the primary rocks ? 74. Of the secondary ? 75. 

 Of the tertiary ? 76. 



What do we find above the tertiary rocks? 77. What is 

 drift? 77. Where is this found? 77. Whence did it come? 77. 

 From how far ? 77. 



What has been formed above the drift ? 78. By what causes ? 78. 



Which of the formations then is most recent? 79. Which 

 next? 79. Which next? 79. Which next? 79. Which is the 

 lowest of the stratified rocks? 79. On what do these rest? 79. 



Are there some portions of igneous rocks above and among 

 the stratified ? 80. Whence do they seem to have come ? 80. 



Have we reason to beheve that the earth was created in the 

 form in which it now is? 81. Is there reason to believe that dif- 

 ferent portions of the earth's crust were formed at periods remote 

 from each other ? 82. 



From what are all soils formed ? 83. Do we know when the 

 drift period was ? 83. Describe its action ? 83. 



What of the loose materials on the earth's surface ? 84. Do 

 soils come from the underlaying rock? 84. Whence do they 

 come? 84. 



How many simple minerals constitute the mass of known 

 rocks? 85. What are they? 85. What are the binary compounds 

 in rocks ? 86. / , 



