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FIRST YEAR SCIENCE 



upon the shrinking interior. The cooling of the earth is 

 so slow that the folding under ordinary conditions disturbs 

 the surface but little. 



42, Rock Weathering. Experiment 42. Weigh carefully a 

 piece of dry coarse sandstone or coquina. Allow this to remain 



in water for several days. 

 Wipe dry and weigh again. 

 Why has there been a 

 change in weight ? 



Experiment 43. Fill a 

 test tube or small glass dish 

 about Jialf full of limewater, 

 made by putting about 2 

 ounces of quicklime into a 

 pint of water. Blow from 

 the mouth through a glass 

 tube into the limewater. 

 There is formed in the lime- 

 water a white substance 

 which chemists tell us is of 

 the same composition as 

 limestone. 



ROCKS WEATHERING AND FORMING DEEP 

 SLOPES. 



Experiment 44. Con- 

 tinue to blow from the 

 mouth for a considerable 

 time through a tube into a dish of limewater. The white sub- 

 stance disappears. A gas in our breath called carbon dioxide dis- 

 solves in the water, forming a weak acid and causes the change. 

 Now if we heat the water, thus decomposing the acid and driving 

 out the gas, the white substance again appears. This gas is found 

 everywhere in the air and is given out in the decay and burning of 

 substances. 



Rocks which are exposed to the atmosphere, especially 

 in moist climates, undergo decomposition. If the climate 

 is warm and dry, rocks may stand for hundreds of years 

 without apparent change, whereas the same rock in another 



