Thus farre of the first part of this element: The second, that like figurs have a meane, proportional lesse by one, then are their dimensions, shall be declared by few words. For plaines having but two dimensions, have but one meane proportionall, solids having three dimensions, have two meane proportionalls. The cause is onely Arithmeticall, as afore. For where the bounds are but 4. as they are in two plaines, there can be found no more but one meane proportionall, as in the former example of 8. and 18. where the homologall or correspondent sides are 2. 3. and 4. 6.
Therefore,
| 2 | 3 | 4 | 6 |
| 3 | 4 | ||
| 8 | 12 | 18 | |
Againe by the same rule, where the bounds are 6. as they are in two solids, there may bee found no more but two meane proportionalls: as in the former solids 30. and 240. where the homologall or correspondent sides are 2. 4. 3. 6. 5. 10.
Therefore,
| 2 | 4 | 3 | 6 | 5 | 10 |
| 4 | 3 | ||||
| 6 | 12 | 24 | |||
| 24 | 5 | ||||
| 30 | 60 | 120 | 240 | ||
