Mr. William Phillips on the OxydofTin. 375 



PI. 26, and as fig. 222 is composed of four equal parts of macles 

 similar to fig. 223, it will follow that the lines a^ b. and ^, r, fig. 224, 

 will represent that portion of the whole plane, occupied by the con- 

 stituent part of one made, and further, the lines of section, a b and 

 b r, being perpendicular to the lines a d and c d^ that the section of 

 each of the four macles constituting that described by fig. 222, takes 

 place parallel with the planes of the common prism ; and it has 

 been shewn, in treating of the primitive crystal, that in this direction 

 a cleavage is easily obtained. 



Those described by figs. 225 and 226 differ only from fig. 222, in 

 this, that the planes of some other modifications are visible, the re- 

 spective numbers of which are placed on them. 



That described by fig 227, consists of four macles similar to that 

 delineated by fig. 211, except that in this, each is elongated in the 

 direction shewn by fig. 228. Fig 229 represents one composed of 

 four elongated macles fig. 214. 



By fig. 230, PI. 26, is represented a singular combination of the 

 four macles composing the preceding figure, placed on the edges of the 

 prism of a crystal similar to fig. 42, pi. 17. This combination may 

 be quoted in evidence to the truth of what has been said of the con- 

 struction of common macles, for it will be observed that the faces 

 1, 1, on the prism of the crystal itself, and on the macles placed on 

 its edges, are all planes of the first modification. Both terminations 

 of fig. 230, as well as of the two preceding figures are visible on the 

 macles. 



Fig. 231, PI. 26. represents a made composed of 16 portions of 

 the prism, fig. 196, PI. 24, each elongated, the whole forming an 

 octangular prism, of which a horizontal section is described by 

 fig. 233. The strias are uniformly in the direction represented. 

 The construction of this made will be obvious by consulting fig. 



