306 ApPENDrx. 



— a a are little glass tubes to hold the wires by, — v is a glass 

 plate on which the ends of the wires are to be brought to- 

 gether. 



LESSON 76. 



Mineralogy. Werner divides the external characters of 

 minerals into two kinds, namely, general and particular. 

 The general characters are the following: 1. Colour; 2. 

 Cohesion ; 3. Unctuosity ; 4. Coldness ; 5. Weight ; 6. Smell ; 

 7. Taste. The particular characters are the following: 1. 

 Aspect of the surface; 2. Aspect of the fracture; 3. Aspect 

 of the distinct concretions ; 4. General aspect ; 5. Hard- 

 ness ; 6. Tenacity ; 7. Frangibility ; 8. Flexibility ; 9. Ad- 

 hesion to the tongue ; 10. The sound. 



General Characters. I. The colours of minerals are ex- 

 tremely various. Werner conceives eight fundamental co- 

 lours, and describes all the others as compounds of various 

 proportions of these. The fundamental colours are, 1. Snow 

 white. 2. Ash grey. 3. Velvet black. 4. Berlin or Prus- 

 sian blue. 5. Emerald green. G. Lemon yellow. 7. Car- 

 mine red. 8. Chestnut brown. II. With respect to cohe- 

 sion, minerals are either solid, f?'i able, or fluid. III. With 

 respect to unctuosity ,v[\mexs\s2Lxe distinguished mio greasy, 

 and meagre ; the first have a certain degree of greasiness in 

 the feel ; the second not. The other four general charac- 

 ters require no particular description. 



Particular characters. I. In the aspect of the surface of 

  a mineral, three things claim attention. L The shape of 

 the mineral. 2. The kind of surface. 3. The lustre of the 

 surface, which is either splendent, shining, glistening, glim- 

 mering, or dull. II. When a mineral is broken, the new 

 surface exposed is called the fracture. Three things claim 

 attention: 1. The lUstre of the fracture. 2. The kind of^ 

 fracture. 3. The shape of the fragments. III. Distinct 

 concretions are distinct masses, which may be separated from 

 each other, without breaking through the solid part of the 

 mineral, by natural seams. Three particulars with respect 

 to these are, 1. Their shape. 2. Their surface, 3. Their 

 lustre. IV. Under the headof ^ener«/ aspect, three particu- 

 lars are comprehended, 1. The transparency . 2. The streak. 

 3. The soiling, or the stain left when rubbed. V. Minerals 



