135 



accurate conception of liis Pyramid of derivation, examples 

 of the mode in which it is constructed. 



When n = I there is one flat, When n = 2 there is one flat, 

 viz. viz. 



1,2 



2, 3 2, 4 

 2, 4 3. 4 



Let « 3c 3, there will be two Let w = 4, there will still be 

 flats: two flats onlv : 



2,3 



2, 3 2, 4 

 2, 4 3. 4 



