Not all writers attributed the action of the tides to the moon. Most significant among the opponents of the lunar theory was Paul the Deacon (720–780 A. D.). In his _Historia gentis Langobardorum_ he described[273] the maelstrom on the coast of Norway. He asserted that this gigantic whirlpool and another one, which he placed off the coast of Ireland, made the tides by sucking in and spewing out vast quantities of water twice a day. With the fashion of reading Macrobius a theory became popular that the flood and ebb result from the impact of opposing ocean currents; and in the twelfth century, as we shall see later,[274] William of Conches and Giraldus Cambrensis made curious combinations of the theories of Paul the Deacon with those of Macrobius. THE LANDS There was no science of geomorphology in the Middle Ages. The medieval mind interested itself for the most part only in those natural phenomena that force themselves upon the attention or seem out of the ordinary. Commonplace and static elements of the earth’s surface such as hills, valleys, and plains were taken more or less for granted by those who sought to explain the secrets of Nature. In the geographical writings of the period, on the other hand, not a little space was devoted to volcanoes and earthquakes. Their violent and spectacular qualities have made these the object of interest throughout all time. And yet in the early Middle Ages there seems to have been no originality in observing them or in speculating about their causes. Men were content uncritically to accept what classical writers had said.[275] Isidore, for example, following Aristotle and Pliny, wrote that volcanoes were burning mountains rather than vents for deep-seated terrestrial fires and that the whole of Sicily was filled with seams of sulphur and bitumen, readily kindled by the winds into flame. The eruption of Etna, more especially, was caused by winds driven down into the interior of the earth by the waves of the Strait of Messina.[276] This theory of vulcanism was reiterated by Bede, Dicuil, and the multitude who copied from Isidore’s work. Other writers explained volcanoes as the outlets of profound subterranean fires,[277] a view fostered by Plato and one that gained authority in the minds of many of the Church Fathers as well as of laymen through the widespread belief, derived from classical mythology[278] as well as from the Bible, that the heart of the earth is the seat of Hell.[279] _THE MEDIEVAL ATTITUDE TOWARDS LANDSCAPE AND SCENERY BEFORE 1100 A. D._