SCIENTIFIC AND PRACTICAL AGRICULTURE. 24l 



Will you describe quartz ? 87. Felspar ? Mica ? Hornblende ? 

 Carbonate of lime ? Talc? Serpentine ? 87. What part of the 

 ponderable matter of the globe is oxygen ? 89. What part of 

 its crust is silica ? 89. What is silica ? Table I. How much of 

 its crust is alumina ? 89. What is said of potash, or potassa ? 89. 

 Of soda,? 89. Of lime and magnesia ? 89. Of iron ? 89. Of 

 manganese? 89. 



What does Dr. Dana say rocks are? 90. What is quartz? 91. 

 Felspar and mica? 91. Hornblende? 91. Talc and serpentine ? 

 91. What are silicates ? Table II. What is said of the quantity 

 of silica in soils ? 



Jp which rocks is there more silica? 92. In which more 

 magnesia, alumina^and Hme ? 92. Are rocks a good criterion of 

 soils? 92. 



How do soils generally produce when first cultivated? 93. 

 On what does their continuance of fertility depend ? 93. 



Describe the action of a torrent in depositing its coarser and 

 finer matter ? 94. Have other causes done the like on a larger 

 scale ? 94. What is the consequence ? 94. 



Which lands should we cultivate first? 95. Is it probable that 

 poorer lands may pSy well hereafter ? 96. 



What is said of reclaiming lands ? 96. By what should farm- 

 ers be guided ? 96. Has science don'e'^any thing for other em- 

 ployments ? 96. What science especially deserves the farmer's 

 attention ? 97. Why ? 97. 



What was thrown up by the most ancient volcanoes ? 98. • 

 What by those more recent ? 98. What by the most recent and 

 by those now in operation ? 98. How does the temperature be- 

 come as we descend into the earth ? 98. At what rate does it 

 become warmer? 98. What do we infer from this? 98. 



At 40 or 50 miles deep what might we expect to find ? 98. 

 What next above the lava? 98. What above the trap? 98. 

 What above the granite ? 98. Name all the formations above the 

 granite, beginning with the primary? 98. Do each of these last 

 form an entire layer around the whole «arth ? 98. Explain the 

 reasons ? 98. On what may the cultivable soil lie ? If it lies on 

 granite, what is that region called ? 98. If on primary rocks ? 98. 

 If on secondary ? 98. If on tertiary ? 98. If on alluvial ? 98. 



Of what does soil consist ? 99. What rock must it have origina- 

 ted from ? 99. Whence did all the igneous rocks on and near the 

 earth's surface come ? 99. What changes have befallen them from 

 the time of their emission from the earth ? 99. What has been 

 mingled with them, to form a soil fit for cultivation, containing 

 the organic as well as the mineral ingredients ? 99. Do we 

 know all the agencies by which the Almighty prepared the 

 soil for man ? 99. What were some of his agents ? 99. Did Grod 

 make the earth a garden ? 99. What did he make it capable ot 

 becoming by human agency ? 99. 

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