It must now be determined how we are to reckon these walls: if we stand in a room with our back to the windows, the first wall is on our left, the second before us, the third on our right, and the fourth behind us. We shall, however, commence with the floor, and divide it into nine parts in the same manner as the walls. Where are 10, 20, 30, 40, etc. to be placed? Every decade begins a new series, and the decimal is placed on the cieling of the room over its proper wall; thus, the first decimal, or 10, will be over the first wall; the second decimal, or 20, will be over the second wall; the third decimal, or 30, will be over the third wall; the fourth decimal, or 40, will be over the fourth wall; the fifth decimal, or 50, as its tenth part exceeds the number of walls, will be assigned to the cieling of the room, and will consequently be the highest number in the first room, forming the connecting link between this room and the second.
