OF NATURAL PHILOSOPHY. 241 



ative or secondary forms. Mohs and others have 

 since imagined processes and systems by which the 

 derivation of forms from each other is facilitated, 

 and have corrected some errors of over-hasty gener- 

 alization into which their predecessors had fallen, 

 as well as advanced, by an extraordinary diligence 

 of research, our knowledge of the forms which the 

 various substances which occur in nature and art 

 actually do assume. 



(263.) In what manner a variety in point of ex- 

 ternal form may originate in a variety of figures 

 in the ultimate particles of which a solid is com- 

 posed, may very readily be imagined by considering 

 what would happen if the bricks of which an edifice 

 is constructed had all a certain leaning or bias in 

 one direction out of the perpendicular. Suppose 

 every brick, for instance, when laid flat on its face, 

 with its longer edges north and south, had its eastern 

 and western faces upright, but its northern and 

 southern ones leaning southwards at a certain in- 

 clination the same for each brick; a house built 

 of such bricks would lean the same way, if the 

 bricks fitted well together. If, besides this, the 

 eastern and western faces of the bricks, instead of 

 being truly upright, had an inclination eastward, the 

 house would have a similar one, and all its four 

 corners, instead of being upright, would lean to the 

 south-east. Suppose, instead of a house, a pyramid 

 were built of such oblique bricks, with the sides of 

 its base directed to the four points of the compass ; 

 then its point, instead of being situated vertically 

 over the centre of its base, would stand perpendi- 

 cularly over some point to the south-east of that 



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