374 Mr. William Phillips on the Oxyd of Tin. 



perfect dodecahedrons, the incidence would necessarily be 120% 

 Supposing the macles represented by fig. 188, pi. 24, or fig. 208, 

 pi. 25, to consist of four sections similar to fig. 196, the plane that 

 would be given to the upper and lower faces by a horizontal section, 

 would resemble fig. 202, the angles of which are 112°. 10', and it 

 will be obvious that this figure could not be made to agree with the 

 plane of section of the perfect dodecahedron fig. 107, the angles of 

 which are 120°, by adding to it triangles of a similar description. 



Macles of Macks, 



The figures in this series occupying pi. 26, are extremely com- 

 plex, as except the latter, each consists of four, or a greater number 

 of similar parts of some one of the macles already described, for 

 which reason I have termed them macks of macks. 



That which is described by fig. 222, PI. 26, consists of four similar 

 parts of macles, fig. 188, PI. 24, which by fig. 223, PI. 26, is placed 

 in such a position as to shew that section of fig. 188, which forms 

 one-fourth part of fig. 222, as will be readily seen by noticing the 

 figures 1, 1, on each, the planes on which they are placed, being 

 those of the first modification, or in other words, of the common 

 prism. The strise on these macles uniformly take the direction 

 given by the lines on fig. 222. I have several that shew both ter- 

 minations, and the natural joints of the four portions of which they 

 are constituted are always visible on the direction of the stronger 

 lines down the center of the faces of what may be termed the prism 

 of the made. As the incidence of the planes 1 , on 1 of this made, 

 give by the common goniometer exactly 90% it follows that a 

 horizontal section of this made would give a square plane to 

 each part so divided. Let this plane be represented by fig, 224, 



