20 PYEAMIDAL SYSTEM. afford the sixteen arrangements contained in the annexed table. IffTeS ™ d 7 8 18 Zer °’ ° r When h = tbe indices h k ;« C +i, 18 zero ’ and ^ = k, or when one of the «. ^11 fe ; “ e ” umber ^ b “ *>”■ Wh»a i and * hkl hkl k h I Hi hkl hkl k h I k hi k h I k h I hkl A k I k h I k h I hkl hkl 66. If we suppose h to be FIG. 29. gitmer tftan A, the annexed fagure will represent the ar rangement of the poles of the form Mel on the surface of the sphere of projection. bv 6 nn / 0rm bound ed either by all the faces of the form hkl H ™ have an odd number of ' positive indices, or by all the aces of the form Mel which have an odd number of nega- herl U ?' ■?! - 18 said to be hemi- hedral with inclined faces, and any one of itefaces^ 6 Symbo1 Md ' where hM is tlle 8 y mb ol o secourl S ^ bcd8 °f the faces of jchkl are contained in the first am of the table^n^os)^ 036 ^ and fourth column; eight^riannh^K ° f the . s P bere of projection be divided inti ooi and loo the n ^' orie '“ rclea through the poles of the formi triangles “ke of Km ° f wiU be found in four alternat < poles of the ^ T alternate triangles. contamcd in the remaining fo kh<y^~' ^vjTo / r, ihl f hhl. • o/7; Ihl ; T , \ ^ ; i hl Wo hit• .am \ •hot 001 \ hoi* |ioo m- ■hkl j V kht j \ khl fi>.. o hi • 'hhl /Mo khl / yf 110 oio -—^0 with inclined faces Jif- e 1 m . adm its of a second hemiliedral fori form hkl in which tho ^ 18 boun( led by all the faces of tl: and which will be <lenr>f r i ^ changes with the sign of symbol of any one of its°f ^ 8 y m hol Xhkl, where hkl is tl; form Xhkl arLontal S * The ^^bols of the faces of tl, of Xkhl in the second andthM ^ aiul f° urt h columns ; tliot If the tabl* («)• sphere of projection bo divided in
