KINDS OF ROCKS 



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EXERCISE 78 

 WEATHER MAPS 



Material. Weather map. 



a. Get a weather map from the Weather Bureau. Paste it 

 in your note book. What is the lowest pressure shown on the 

 map? The highest? Where are the "lows" of the map, that 

 is, in what states? The "highs"? 



b. What is the difference in pressure, in inches, between two 

 successive isobars (lines of equal pressure)? What happens 

 when the isobars are close together? See 274 of the text. 



Are there any lines of equal temperature (isotherms) on the 

 map? For what temperatures are they given? Why are they 

 so irregular? 



EXERCISE 79 

 KINDS OF ROCKS 



Apparatus and Materials. Pocket knife, cent, triangular steel file; 

 the substances named in a; hydrochloric acid. 



a. Examine a piece of each of the following materials : sand- 

 stone, marble, limestone, rock salt, soft coal, hard coal, shale, 

 conglomerate, quartz, feldspar, granite, glass, soapstone, slate, 

 brick, pumice, concrete, gypsum. 



