V.JL 



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TABLE OF CONTENTS. 



DEFINITIONS. . . 



The object of the science . .... ....... .,. . >** '-twi* <: I 



A crystal, what 1 



Its planes, edges.., and angles 1 3 



The value of an angle how determined . . 2 



Crystals formed of homogeneous molecules ......... 5 



The same mineral crystallises in a variety of forms .w^.itt 



These forms are primary * * v**:*i..v4'4 * ' 



or secondary -.. <., .**,&* y.<jf" 



What a primary form is ...,,*, * -. . 



Classes of primary forms 6 1 1 



Secondary forms .......,* --*ba ')% . . 11 



Diagonal of a plane 12 



Diagonal plane of a solid 12 



Axis of a crystal 1 2 16 



Crystals when in position 17 



[ V . how formed 17 



. * . . increase by the additions of plates of molecules 18 

 .... . preserve their, original form when the added 



QTf plates are entire 18 



.... the original form altered when the added plates 



...... k , are defective 18 



' . , , , .alteration said to be produced by decrements 



L on the edges or angles 19 



Decrements, why so termed 19 



their nature and character 19 23 



Law of a decrement ** 4 * *> * . . . 24 



Tangent plane 24 



OF THE GONIOMETEH AND THE METHODS OF USING IT 25 32 



GLNEUAL VIEW or THE SUBJECT 33 



MOLECULES OF CKYSTALS 36 



are particular solids .; * 3$ 



their fonns , 3852 



STRLXTLRE, illustrated by the crystallisation of common , ; 



CcS salt . .. 53 5 



