236 DISSERTATION IV. ON THE GEOLOGICAL CHANGES IN ST. PAUL'S BAY. In attempting to identify places on the sea coast with the descriptions or notices in ancient authors, we must always take into account the geological changes which may or must have taken place in the interval.* Such changes must be owing to one or other of the following canses: First, Violent disturbances, such as would affect the configuration of the land. Second, Movements of elevation or depression. Fourth, The siltage of the disintegrated matter. With regard to the first of these causes, there is no reason to suppose that any change has been produced by these since the island has been inhabited by man. * Major Rennel is, if I mistake not, the first author who pointed out the necessity of this in his paper " On the Place where Julius Cæsar landed in Britain." (Archæologia, p. 499.) Captain Copeland, R. N., who states that he is not a geologist, speaking of the sea coast of Megara, says, "The localities described by Thucydides do not agree in any one particular with the present features of the coast." (Arnold's Thucydides, ii. 396.) My friend, Captain Spratt, R. N., who is a geologist, has proved, that if we allow for the necessary changes, the notices of Thucydides agree perfectly with the localities. See Journal of Geographical Society, viii. 205. Nor is there any reason to suppose that any movement of elevation has taken place within the same period. There has, however, been a slight movement of depression within the human period, but it belongs to a remote antiquity, anterior, in all probability, to the time of the shipwreck. That such a movement has taken place is proved by the tracks of wheels, not connected with existing roads, which are deeply impressed on the upper surface of the rocks, and are seen at different points of the island to pass under the sea. * There is, however, a geological proof that the extent of this change of level has been very small, and not sufficient to have produced any perceptible change on the relative positions of the soundings, and of the headlands and shores. of the bay. The proof is this: In the narrow channel which separates the sea, on the outside of Selmoon Island, from St. Paul's Bay (a place where two seas meet), there is to be seen under water a vertical escarpment, running across from the island to the mainland (see dotted line on chart), which is evidently an ancient sea cliff, and which must have been scooped out by the action of the sea, during the period of stationary level which preceded the present. From the transparency of the water, it can easily be observed. I estimate the change of level which this appearance indicates at ten feet. In Captain Smyth's chart the difference in the soundings on each side of the escarpment is two fathoms, which agrees very well with my estimate. If we * See a paper by the Author on Recent Depressions in the Land, Journal of the Geological Society, Aug. 1847, p. 235. assume that the depression has taken place since the shipwreck, it would make only a slight change in the absolute position of the soundings, and of the two headlands of the bay; but none at all in their relative positions. The point of Koura, before the last depression, must have extended farther to the north, but so must the line of twenty fathoms. The point of Salmonetta, or Selmoon Island, must have extended farther to the east; but the line of fifteen fathoms must have been just so much farther to the east ; hence the reasoning in both cases would be the same. It is only necessary to look at the dotted line parallel to the coast, which marks the depth of three fathoms, to show that a much greater change of level than what has actually taken place would make but a trifling alteration in the contour of the shores of the bay. If, then, the depression did take place since the shipwreck, the conclusions to be drawn from the comparison of the locality with the narrative would be the same. The only effect which the wasting action of the sea could have, would be that of rendering it impossible to ascertain the exact point of appulse of the ship when she was run ashore; but this I have not attempted to do. In every other respect, an allowance for the changes arising from this cause strengthens the conclusions we draw from the present state of the coast. The shore from Salmonetta Island to Mestara Valley is now girt with mural cliffs, where a ship could not be stranded with safety; but there is a creek in this line of cliff, now without a beach, but which we know, from the form of the land, must at one time have had a beach which has been worn away in the course of ages, by the wasting action of the sea. The degradation of the land actually taking place at this point is proceeding with more than usual rapidity, owing to the inclination of the beds, and the tendency which large fragments of the rock have to fall over when undermined by the sea.* I therefore think it not improbable that the beach existed at the time of the shipwreck. If so, this creek, which, as may be seen on the chart, is immediately to the south of the place which Captain Smyth has marked as the traditional place of the wreck, agrees perfectly with the spot where a ship from the eastward anchored in the entrance of the bay would be driven in a gale from the E. N. E. (Euro-aquilo), and is close to a place where two seas meet. The rate of siltage at the bottom of the sea must, from the structure and size of the island, be extremely slow. The rocks disintegrate into minute particles, which are of course carried by the action of the waves and the currents to a great distance, before they are finally deposited on the bottom of the sea. There is but little alluvium washed down by streams from any part of the island; and at St. Paul's Bay there is scarcely any. The surface of the island, which is very flat, is composed of a series of beds of tertiary rock, which overlies a thick stratum of clay. The superincumbent rock is much fissured. The rain, which falls on the surface, passes through the fissures, is * Abela, who wrote in 1642, states, on the authority of an ancient manuscript, that the ruins of the residence of Publius, the chief man of the island, stood here. He says: "Villam hospitalem S. Publii, vicinam rupibus dithalassis quibus (Act. 27.) navis Pauli quassata maris tempestate stetit impacta donec solveretur a fluctibus, fuisse in clivo ad orientem ac septentriones adversum," &c.—p. 230. absorbed by the clay, and finally reappears in springs. No stream flows into St. Paul's Bay, except one which issues from a translucent spring, which the natives term "Ayn tal Razzul," or "The Apostle's Fountain," a name which proves the great antiquity of the tradition; for the signification of the Phoenician word Razzul (Apostle) is unknown to the Maltese.* During the excavation of the dry docks at Valetta, my friend, Mr. John Anderson, of the engineer department, paid particular attention to the phenomena, from which the amount of siltage during the human period could be deduced. According to his report, in that branch of the harbour of Valetta, works of art are not found more than six or eight feet below the present bottom of the sea. But the deposit there must be much more rapid than in any part of St. Paul's Bay. The dock is situated in a deep inlet, at the mouth of an extensive valley, and its shores have been from the earliest times the site of a town. In such a situation, the rate of siltage must have been much quicker than in the comparatively shallow inlet of St. Paul's Bay, where none * 66 Fons Paulinianus ex arenti solo in mare profluit cui nomen Ayn tal Razzul ignota nunc indigenis significatione nominis; at Tyris et Phoenicibus fontem Apostoli sonat."-Quoted from an ancient MS. by Bres, a Maltese: Malta Antica Illustrata, p. 395. On a stone near this fountain there are inscribed, or rather were, for I was unable to discover them, the following lines, which I give from Bryant (p. 67.).— "Hac sub rupe cava, quam cernis ad æquoris undas, Exiguus trepidat fons salientis aquæ, Religione sacra latices venerare, viator; Naufragus has dederit cum tibi Paulus aquas." |