Earth Study 837 



5. Test a piece of limestone for hardness. Can you scratch it with a 

 knife? Is it as soft as marble ? Put on it a drop of acid. Does it effer- 

 vesce? If there are any fossils in your piece of limestone, test them with 

 acid and see if they will effervesce. Any other mineral that you have which 

 will effervesce when touched with acid, is probably some form of calcite. 



6. Are there any buildings in your town made of limestone ? How do 

 you know the stone is limestone ? Where was it obtained? Is it affected 

 by the weather? 



7. Is limestone a good material for making or mending roads? Give a 

 reason. 



8 . Why is water in limestone regions hard ? Why are limestone regions 

 likely to have caves within the rocks ? How are stalactites and stalagmites 

 formed in caves ? What are sink holes ? How are they formed ? In what 

 county of your state is limestone found ? 



9. How is the lime which is used for plastering houses made? 



10. Write a theme on how the chalk rocks are made? 



11. Test a shell with acid; test a piece of coral with acid. How does 

 it happen that these, which were once a part of living creatures, are now 

 limestone ? Of what are our own bones made ? 



"A great chapter in the history of the world is written in the chalk. Few passages in the 

 history of man can be supported by such an overwhelming mass of direct and indirect evi- 

 dence as that which testifies to the truth of the fragment of the history of the globe, which I 

 hope to enable you to read, -with your own eyes, to-night. Let me add, that few chapters of 

 human history have a more profound significance for ourselves. I weigh my words well 

 when I assert, that the man who should know the true history of the bit of chalk which every 

 carpenter carries about in his breeches-pocket, though ignorant of all other history, is likely, if 

 he will think his knowledge out to its ultimate results, to have a truer, and therefore a better, 

 conception of this wonderful universe, and of man's relation to it, than the most learned, 

 student who is deep-read in the records of humanity and ignorant of those of Nature." 



"During the chalk period, or 'cretaceous epoch, 1 not one of the present great physical 

 features of the globe was in existence. Our great mountain ranges, Pyrenees, Alps, Hima- 

 layas, Andes, have all been upheaved since the chalk was deposited, and the cretaceous sea 

 flowed over the sites of Sinai and Ararat. All this is certain, because rocks of cretaceous 

 or still later date, have shared in the elevatory movements which give rise to these mountain 

 chains; and may be found perched up, in some cases, many thousand feet high upon their 

 flanks" 



THOMAS HUXLEY. 



