The diagram (Fig. 6) represents a block of 27 cubes, which form Set 1 of the 81 cubes. The cubes are coloured, and it will be seen that the colours are arranged after the pattern of Model 1 of previous chapters, which will serve as a key to the block. In the diagram, G. denotes Gold, O. Orange, F. Fawn, Br. Brown, and so on. We will give names to the cubes of this block. They should not be learnt, but kept for reference. We will write these names in three sets, the lowest consisting of the cubes which touch the table, the next of those immediately above them, and the third of those at the top. Thus the Gold cube is called Corvus, the Orange, Cuspis, the Fawn, Nugæ, and the central one below, Syce. The corresponding colours of the following set can easily be traced. Olus Semita Lama Via Mel Iter Ilex Callis Sors Bucina Murex Daps Alvus Mala Proes Arctos Mœna Far Cista Cadus Crus Dos Syce Bolus Corvus Cuspis Nugæ Thus the central or Light-buff cube is called Mala; the middle one of the lower face is Syce; of the upper face Mel; of the right face, Proes; of the left, Alvus; of the front, Mœna (the Dark-blue square of Model 1); and of the back, Murex (the Light-yellow square). Now, if Model 1 be taken, and considered as representing a block of 64 cubes, the Gold corner as one cube, the Orange line as two cubes, the Fawn point as one cube, the Dark-blue square as four cubes, the Light-buff interior as eight cubes, and so on, it will correspond to the diagram (Fig. 7). This block differs from the last in the number of cubes, but the arrangement of the colours is the same. The following table gives the names which we will use for these cubes. There are no new names; they are only applied more than once to all cubes of the same colour. {Olus Semita Semita Lama Fourth{Via Mel Mel Iter Floor.{Via Mel Mel Iter {Ilex Callis Callis Sors {Bucina Murex Murex Daps Third {Alvus Mala Mala Proes Floor.{Alvus Mala Mala Proes {Arctos Mœna Mœna Far {Bucina Murex Murex Daps Second{Alvus Mala Mala Proes Floor.{Alvus Mala Mala Proes {Arctos Mœna Mœna Far {Cista Cadus Cadus Crus First {Dos Syce Syce Bolus Floor.{Dos Syce Syce Bolus {Corvus Cuspis Cuspis Nugæ [Illustration: Fig. 6.] [Illustration: Fig. 7.] [Illustration: Fig. 8.]