It would be easy to write much more about primitive swing bridges, but enough has been said to stimulate thought and discussion. Not one of them has a brighter intelligence than that which we find in many prehistoric handicrafts.
VIII
NATURAL ARCHES—THEIR SIGNIFICANCE AND THEIR INFLUENCE
Long before the germ of humanity in some anthropomorphous apes became slowly fertile in a mysterious gestation, Nature had weathered many rocks into hollowed and vaulted shapes. Some were yawning sea-caves, whose arched mouths gulped in the tidal waves, and whose caverned bodies gurgled or boomed with the noise of deepening water.[55] Others were vaults gradually fretted into being by subterranean torrents, such as we find to-day at Saint-Pons, in the Cevennes, where the river Jaur is nourished by an abundant spring which in a second, through the mouth of a low-arched cavern, pours a thousand litres of fresh, sweet water. Others, again, were genuine arched bridges, such as we find to-day in the Pont d’Arc, over the river Ardèche ([p. 6]). In England we have several such bridges, notably the Durdle Door on the coast at Lulworth, whose arched span must owe at least a part of its shape to the troubled action of sea-waves. “La Roche Percée” at Biarritz—a crinkled, lava-like formation—is inferior to our Durdle Door; and “La Roche Trouée,” near Saint-Gilles Croix-de-Vie, though remarkable as a square-headed aperture, has a lower place still in the pontine work done by Nature.[56]
Perhaps the most wonderful rock-bridges are those at Icononzo, in New Grenada, over the torrent of Summa-Paz. There are two, and one of them soars up and up to a crown that spans the water at an altitude of ninety-seven metres. How could men of genius fail to be architects when Nature set before their eyes great vaults, not only varied in shape, but at times of a stupendous height? In different ways she produced surbased arches, pointed arches, semicircular arches, all more or less ragged in their outlines, but each a model for progressive mimicry and adaptation.
Here is not the place to dally with the causes of their formation, such as uneven weathering and the scour of running water subject to high tides or to terrific floods. As rivers in the course of many ages deepen and widen their channels, they reach now and then a strata of fissured rock, and their eating action is very rapid when they are able to undercut the softer rocks by fretting their way along apertures or crevices. Many an earthquake has made such inlets for river water, and earthquakes may have shattered some rocks into vaulted shapes. Whether glaciers have played a part in the hollowing of rocks into arched caves and bridges I do not know; but rock-basins are attributed to the erosive power of glaciers, so why not some rock-bridges also? It is a question over which geologists ought to quarrel as they did over rock-basins.[57]
PONTE DELLA PAGLIA AT VENICE, RENAISSANCE
But the main point is that the archways made by Nature not only suggested the arched bridge of handicraft, but heralded all the lovely styles of building which have used vaults, domes, turrets, towers, spires, steeples, and arched openings—gateways, porches, and windows. There is a rival art, as we know, an art which has glorified the long lintel-stone carried by pillars; but it has never won from the genius of great men the highest technical inspiration. To it we owe much work of a noble dignity, but in the powerful aspiration of this work there is but little upward flight; it is not near at once to the point of heaven and the point of home. In fact, its masterpieces weigh down heavily on the earth instead of rising towards the light. Not till we come to genuine architecture—to the art that employs arches and vaults and domes—do we find united in the same edifice a majestic weight and a buoyant fervour. This union of qualities may be found in a supreme Roman bridge, such as the Puente Trajan at Alcántara, but it reigns most beautifully in a Gothic cathedral, whose bulk, earth-bound and vast, has in it what Goethe defined as a petrified music, lofty and spiritual. Rome built for man and the ages, while Gothic art has a symphonic ardour expressed in a creed of hope that transcends all terrene things.