434 



SCIENTIFIC RECREATIONS. 



trouble. When the fragments of a mineral are held in the flame by platinum 

 " tweezers," or tongs, then the fusibility of the substance, and the colour of 

 the blow-pipe flame will be of great assistance in determining the nature of 

 the mineral. It is also curious to observe the different forms into which the 

 various substances expand or contract under the influence of the blowpipe. 

 We may have a rugged slag, an enamel, or a glass, or a bead, or " drop" of 

 metal. The varied substances produce various colours yellow, green, orange, 

 or red, according to circumstances. Strontia is a vivid red, copper is green, 

 lime orange, and so on. 



It is very little use to attempt a study of mineralogy without some 

 acquaintance with chemistry. In dealing with minerals, and in studying 

 geology, we must try to keep our knowledge of chemical science in our 

 minds, and thus fortified we can more easily understand the steps leading to 



Fig. 456. The blowpipe. 



the classification of minerals. It is impossible to teach mineralogy or geology 

 from books. Nature must be studied, the specimens must be seen, the 

 earth must be examined. The advance in mineralogy may be probably 

 will be slow, but crystals will teach something ; and when we can pass a 

 viva voce examination in chemistry and crystallography, expressing, by the 

 symbols, the various substances under discussion, we shall have made a 

 considerable advance in the science. We shall have an idea of the com- 

 ponent parts of various substances, and be able to class the various minerals 

 according to their chemical constitution. Beginning with the metalloids, we 

 shall pass to the metals and various compounds, salts, resinous substances, 

 etc., such as amber. 



It is impossible in the space at our command to describe all the 

 minerals, and yet it is necessary to enumerate the most important. We 

 may, therefore, take them in the following order. It should be added that 



