174 THE NATURE STUDY COURSE. 



by dividing 8 J ounces by the loss of weight in water, 4 J 

 ounces. 



Chemical Properties. — Not affected by hydrochloric or other 

 acids. Burns giving off gases. 



Composition. — 



Formula. — 



Classification as a Mineral. — These three topics can hardly 

 be studied by the Nature Study method. Items entered in 

 the record that are not discovered by investigation should be 

 credited to the teacher or other source of information. 



Tests. — Color; it burns without melting. Asphaltum 

 resembles coal but it fuses with heat. 



Varieties. — There are many grades between bituminous coal 

 and the brightest, hardest anthracite. Shale, pyrites or other 

 impurities are mixed with coal in some specimens. 



Uses. — The uses that are stated upon the authority of 

 observation or experience should be distinguished from those 

 that are learned second-hand. 



Natural History. — What most pupils will say about the 

 mining and formation of coal will be derived from their 

 reading. The sources should be acknowledged. Pupils should 

 be shown where and how to obtain information in which they 

 are interested but which they cannot discover for themselves. 



Rocks. — The recognition and nature of the commoner rocks 

 should be taught in this connection. Quartz, feldspar and 

 mica can be recognized in many specimens of granite. Gneiss 

 is usually coarser and layered and is of similar composition. 

 Schists, slates and shales are layered rocks. Sandstones and 

 limestones, explained by their names, were laid down in water; 

 specimens of those rocks can often be picked up around 

 buildings in course of construction where stone is used. 



