An indentation of the coast marks the spot where a slender stream descends to the sea through a stretch of white sand; and beyond this the rocky coast rises but slightly above the sea level. Our steps were directed towards the so-called Cave of Hercules. This was originally a mere hollow in the face of the sea cliff; but from a remote period of antiquity it has been quarried for the purpose of extracting the hand-mills universally used in this part of Marocco. These, which are quite the same as the Scotch _querns_, are cut out in the rudest way by hammer and chisel, leaving the surface of the rock marked by a series of circular indentations about eighteen inches in diameter. In this way the original dimensions of the cave have been greatly enlarged, and, as it is still worked for the same purpose, the process is sure to be continued. In connection with the question raised of late years as to change of relative level of land and sea within the historic period, we observed some very ancient markings that showed the works to have been carried somewhat below the present level of high tide; but we could trace none that appeared to reach so low as that of the ebb tide. So far as the evidence at this point goes, it seems to prove a slight amount of submergence during the period for which the rock has here been quarried. This period may probably be reckoned at 2,000 years, and possibly much exceeds that limit. Taken in connection with still existing remains in Greece, Asia Minor, the Phœnician coast of Syria, and Egypt, it tends to show that the changes in the general level of the Mediterranean coasts, indicated by many geologists, must have proceeded very slowly during the historic period, and that the more considerable oscillations, that have undoubtedly occurred near Naples and on the east coast of Sicily, have been mainly due to the local influence of volcanic action. The soil near the cave was much mixed with sand carried by the wind, and the plants seen were chiefly widely diffused species that find tolerably uniform conditions of life on the sandy shores of the west coast of Europe. The rocks near the cave produce samphire and the sea fern (_Asplenium marinum_), just as they do in Cornwall; while _Diotis maritima_ and _Lotus Salzmanni_, a local variety of the widely spread _Lotus creticus_ of Linnæus, were frequent on the sands. The chief ornament was _Statice sinuata_, whose delicate azure flowers were already in blossom, long before most of the species of that late-flowering genus.