11
The first pair of these numbers consists of one and two, the second of three and four, the third of five and six; neither of which pairs make a tetragonal number, either by themselves or joined with any other figures. The fourth consists of seven and eight, which, being added all together, produce a tetragonal number of thirty-six. But the quaternary of numbers set down by Plato have a more perfect generation, of even numbers multiplied by even distances, and of odd by uneven distances. This quaternary contains the unit, the common original of all even and odd numbers. Subsequent to which are two and three, the first plane numbers; then four and nine, the first squares; and next eight and twenty-seven, the first cubical numbers (not counting the unit). Whence it is apparent, that his intention was not that the numbers should be placed in a direct line one above another, but apart and oppositely one against the other, the even by themselves, and the odd by themselves, according to the scheme here given. In this manner similar numbers will be joined together, which will produce other remarkable numbers, as well by addition as by multiplication.
