On Crystallography. 9^1 



this lamina above the preceding, in such a manner that the 

 points t", a", i', o", may answer to (he points </, a', i', o', 

 (fig. B) leaving the squares empty which have their exter- 

 nal angles situated in Q, S, R, P, V, '\\ M, G, Sec, and 

 continuing to eflVcl the decrement by a row. We also see 

 here that the solid increases successively towards the analo- 

 gous edges at EA, EO, A I, O f, (fig. A) since between 

 B and H, tor example, (fig. C) there are thirteen squares, 

 uistcad of there beina; only eleven between Q V and LC, 

 (fig. B) ; but as the effect of the decrement confines more 

 and more the surface of the laminae in the direction of the 

 diagonals, nothing else is wanted than to add towards the 

 unchanging edges a single cube denoted by B, K, H, or D, 

 (fig. C) instead of the five which terminate the precedinjr 

 lamina, along the lines O V, PN, LC, FG, (fig. B.) 



The great faces of the laminas of superposition w hich 

 were hitherto octagons OVGFCLNP, (fig. B) having 

 reached the figure of the square B K H D, (fig. C)* will, 

 after passing This point, decrease, so that the following la- 

 mina will have for its great superior face, the square B' K' 

 H' D', (fig. D) which is less by one row in every direction 

 than the square B K H D (fig. Cj : we shall dispose the 

 first above the second, so as to make the points c f It g , 

 (fig. D) answer to the points c,f, h, g, (fig. C.) 



Figures E, F, G, H, represent the four laminae wbicli 

 ought successively to rise above the preceding, with this 

 condition, that the similar letters correspond as above. The 

 last lamina will be reduced to a simple cube denoted byx', 

 (fig. I) and which ought to rest on that represented by the 

 same letter (fig. H). 



It follows from what has been said, that the laminae of 

 superposiiion, when applied on the base EAIO, (fig. A) 

 produce, by the assemblage of their decreasing edges, four 

 faces, v\hich, issuing from the points E, A, I, O, are in-, 

 dined towards each other under the form of a pvramidal 

 summit. 



We must now remark that the edges in question have 

 lengths which commence by increasing, as we mav observe 

 by inspecting figures B and C,and then proceed to dmiinish, 

 as we may judge by the following figures. Hence it results 

 that the faces |)roduced by these same edges go onenlargin"' 

 from their origin to a certain point ; and when past this, 

 tlu-y begin to contract themselves so as to consiitule two 



In the present, case, tti!.; (ijjure takes place ;it the second l;imin:; of r.u.- 

 ositioii. On talcing a nucleus comi)ostd of a yfre.iicr ininiber of mole- 



triangles 



pprposition 



^•llll■^, ii is evi.l.;.it iK/tt we «h<)cl(.l lizve :i more rciiiytc limit 



