This comparative proportion, or, in other words, this attention to scale or measurement, is not only necessary with regard to objects near each other, but it forms the basis of all improvement depending on perspective, by the laws of which it is well known that objects diminish in apparent size in proportion to their distance: yet the application of this principle may not, perhaps, have been so universally considered. I shall, therefore, mention a few instances in which I have availed myself of its effects.