To find the area of any rectilinear figure, various methods are available.
The species of Linnaeus were supposed to represent a series of steps in a scale of ascending complexity, and it was thought possible thus to arrange the animal kingdom in a single series - the orders within the classes succeeding one another in regular gradation, and the classes succeeding one another in a similar rectilinear progression.
Another question to which he devoted much attention was that of obtaining rectilinear motion by linkage.
Associated with these irregular escarpments are occasional rectilinear ridges, the work of extensive erosion on monoclinal structures, of whick Echo Cliffs, east of the Painted Desert (so called from its manycoloured sandstones and clays), is a good example.
With the renewal of uplift by which the earlier cycle of erosion was interrupted and the present cycle introduced, inequalities of surface due to renewed faulting were again introduced; these still appear as cliffs, of more nearly rectilinear front than the retreating escarpments formed in the previous cycle.