Let us now suppose a glass plate placed in front of the Block in its first position. On this plate let the axes X and Z be drawn. They divide the surface into four parts, to which we give the following names ([Fig. 17]):—
Z X = that quarter defined by the positive Z and positive X axis.
Z X = that quarter defined by the positive Z and negative X axis (which is called “Z negative X”).
Z X = that quarter defined by the negative Z and negative X axis.
Z X = that quarter defined by the negative Z and positive X axis.
The Block appears in these different quarters or quadrants, as it is turned round the different axes. In Z X the Moenas appear, in Z X the Alvus faces, in Z X the Syces. In each quadrant are drawn nine squares, to receive the faces of the cubes when they enter. For instance, in Z X we have the Moenas of:—
| Z | |||||
| Comes | Tibicen | Vestis | |||
| Ostrum | Bidens | Scena | |||
| Urna | Moles | Saltus | |||
| X | |||||
And in Z X we have the Alvus of:—
| Z | |||||
| Mars | Spicula | Comes | |||
| Ala | Uncus | Ostrum | |||
| Sector | Frenum | Urna | |||
| -X | |||||
And in the Z X we have the Syces of:—