ON THE METHODS OF DRAWING THE 

 FIGURES OF CRYSTALS. 



THE representation of surfaces, or of solid bodies, 

 upon a plane, is the object of the art of perspective. 

 The theory upon which this art has been founded, 

 supposes an imaginary transparent skreen to be inter- 

 posed between the eye of the observer and the object 

 to be represented ; and it supposes also that the rays 

 of light which pass from the object to the eye through 

 the skreen, should become, as it were, fixed at its sur- 

 face, so that when the object is removed, its figure 

 or representation should still remain apparent on the 

 skreen. And the rules of perspective teach the 

 methods of delineating the figures of objects upon 

 a plane, in such a manner, as to resemble the appear- 

 ance they would present to the eye if seen through the 

 plane on which they are delineated, supposing that 

 plane to be transparent, and held between the object 

 represented and the eye. 



A more familiar conception of the nature of a per- 

 spective representation may be derived from looking 

 at a building, or along a street, through a piece of 

 glass, and marking lines on the surface of the glass 

 coinciding with the lines of the object we are 

 observing through it. These lines, if accurately 

 traced, will evidently represent the object to the eye, 

 such as it appeared when seen through the glass. 



