30 EHOMBOHEDKAL SYSTEM. ana tne other six alternate luucs flm** v n i a_ , the algebraic sum of two nf lu , except when third index. And if the snhp ^dices 1S # equal to twice the twelve triangles by zone-circWh P™J ectl0n be divided into of the forms in 2II sir f U ? h ev “7 tw0 of the P oles poles of Tthkl- and the nf ? en j ate triangles will contain the Trlkh, except when the sum nfV 1 * a ! terllate tnan S les those of 110. The form 1. ? . ™ e mdices is zero. rhave for their symbols the 61 ^ 61, ^ ^ the faces of Mcl which which stand in °r + \ + *> + l ’ which stand in the cr-Ln i t ’ and tlose of ~ h > their symbols the armr 1 " ’ ° r a11 the faces which have for in the order IJchlJc and th” 811 * 8 /’*' \ h ’ + Ic ’ + l ' whicl1 stand in the order °[ ~ h ’ ~ k ’ ~ l > ^ich stand faces, and will be dennfoT'k iiemihedral with asymmetric symbol of any one of its faces where hkl la tho the symbols of C(dli mns of the table in (112) contahi those of alkh. aCes 0 u,l M; the second and third columns lunes by zTm-ciVhL^l sph ® re ,°f projection bo divided into six three alternate lune, J°u S the .P oles of the forms ill and 2I1, remaining three ab-mm * 1 contaln the poles of ahkl, and tho 117 t 7 alternate Junes the poles of alkh. Let o be t^ie™ 1 ' 116 P 08 ^‘ on °f an y P°le. * the pole of m/ 5016 ° f 111 ’ A > B > c the poles of 100, 010, 001; OA = OB = OC — n coa, aob are each equal’ to°m° ^ = AB ’ th ° B0 °’ FIG. At. tanroA = ^3 ^ — I 2X^7X377’ tan pod = I — h tanpoc = ^3 h — ]c 21 ~ FLTI,’ D P rr* +—^tann. n is the angular elemorf 1- rhombohedral system. ° 8 CI 7 8 tal belonging to