Though Donald had never studied mathematics as taught in books or the schools, he was a profound mathematician notwithstanding. Experience had taught him the superiority of the sloping to the perpendicular wall in resisting the waves; and he set himself to discover that particular angle which, without being inconveniently low, resists them best. Every new bulwark was a new experiment made on principles which he had discovered in the long nights of winter, when, hanging over the fire, he converted the hearth-stone into a tablet, and, with a pencil of charcoal, scribbled it over with diagrams. But he could never get the sea to join issue with him by changing in the line of his angles; for, however deep he sunk his foundations, his insidious enemy contrived to get under them by washing away the beach; and then the whole wall tumbled into the cavity. Now, however, he had discovered a remedy. First he laid a row of large flat stones on their edges in the line of the foundation and paved the whole of the beach below until it presented the appearance of a sloping street--taking care that his pavement, by running in a steeper angle than the shore, should, at its lower edge, lose itself in the sand. Then, from the flat stones which formed the upper boundary of the pavement, he built a ponderous wall, which, ascending in the proper angle, rose to the level of the garden; and a neat firm parapet surmounted the whole.--Winter came, and the storms came; but though the waves broke against the bulwark with as little remorse as against the Sutors, not a stone moved out of its place. Donald had at length fairly triumphed over the sea.