374 



J. D. Dana on Cohesive Attraction. 



cated as in fig. 11. To understand this we must study the steps 

 in the process. Fig. 17 represents the same secondary planes as in 

 fig. 1 1, without the primary faces. It is obvious that in the enlarge- 

 ment of such a secondary, when the summit molecule is annexed, 

 its lateral axes do not act as they do when a cube is formed : 

















Fig. 



18. 









f c 







Fig. 17. 



fc 



■ ^r~"~~^^ ^F^^H 



pYc 













^*V jrfi " 1 









^ 



1 lifc: 



4^ 



||l 



1 /_£] 



"^ **^^^^^ ^^B ^fc 



1 "■„ — O- 



Hyc 







Ptf 











1 









^^^^^^ 



I c 



yfi^pS^ c 



















when another molecule is added beyond, then they act laterally. 

 This may perhaps be more clearly seen in the transverse section 

 in fig. 18. When A attracts B, B does not act laterally as in fig. 

 16 ; it does not so act until B attracts 0, when a C is added ei- 

 ther side of B. So C acts laterally when a D is added to C, and 

 not before. 



Again in fig. 19, we have a section of another figure, (the same 

 secondary as in fig. 12,) showing the arrangement of molecules in 

 a solid, presenting such a section. Examining it, we perceive 



Fig. 19. 

















/G 



/ G 



■H ~~~ m 



1 



U=/g 



Y G 



-J 











Jk 





J\~ 



^Jt 





k ']^^E~ 



^"^^^*^_ _^^l ~ 



Y G 



yc 







■^m _ L 



^^■■i^™ ^^~^^^^^w 



-■--■ t -*J^^- 



==7^^| 









that when G is added to the extremity of the central axis, two 

 molecules, G, G, are added on either side of F, and none laterally 

 to G. This figure represents the formation of the secondly 

 plane having the ratio 1 : 2, as is evident from inspection, and ng- 

 17 or 18, another with the ratio 1:1. h 



If the period of time occupied by the union of a moleci lie _ 

 represented by p, then when the lateral axes act only after ^ 

 period of time p, and then add a single row of molecules, tne .^ a 

 condary plane is the truncating plane 1:1; for the plane havj g 

 the ratio 1 : 2, in which two are added laterally to one terminal 

 or what is equivalent, one laterally for every half a one ter y l"f ij' 

 the time would be ip ; for the plane 1 : 3, the time would be sy- 



