The arch was rather of Roman than Grecian invention; and, when composed of a semicircle, its construction belongs rather to perpendicular than to lateral pressure; but in every other arch (except the elliptical and the Catanarean arch) there is a great lateral pressure, and this constitutes the basis, or first principle, of Gothic architecture; to which pinnacles and finials, and other parts, were added for the purpose of strength to the abuttals, although frequently mistaken, and ignorantly copied, as if merely ornamental.