pact bands (scoriaceous both above and below), alternating with each other. Large cavities are occasionally shown, and near these the rock is full of air on the inner surfaces, though the walls inclosing them are often extremely rough and rugged. Where the sea has access, it has taken advantage of the cavities, and has undermined the rock to some extent, but few substances are so well able to resist the action of the waves as compact lava, whether of ancient or modern date. Some expressions occasionally made use of in speaking of lava currents are extremely inaccurate. Such a thing as a flood or rush of lava has never been known in nature. Lava issues but slowly from the earth, and even when it moves down the steepest slope it advances very slowly close to the point of issue. That which overspread Catania moved with unusual rapidity, but it required twenty days to travel its first eleven miles, with an average fall of one in twenty-five. The remainder of the distance (two miles) required twenty-three days more. Even in very rapid flows, at their most rapid rate, four hundred yards an hour, or about twenty feet in a minute, would be an extraordinary pace.* Far more commonly the rate is not more than three or four feet per minute, and often it is very much less. A current of lava, therefore, although it may occasionally do great mischief, can hardly arrive at any spot without ample notice. This is not the case with the ashes and other substances erupted, or with earthquakes. The former are often so abundant and come on so rapidly and unexpectedly that they entirely bury and destroy villages and towns. The latter devastate large areas, and are much more destructive than the lava-currents, commencing, as they do, without any warning. Thus, then, we have in the phenomena that now remain of the Etna eruption of 1669, nearly two centuries ago, a connected history of one of the earliest great volcanic disturbances that has been minutely recorded in modern times. The disturbances commenced with earthquakes, which affected extensive areas. Large quantities of aqueous vapour, and various gases were erupted from long and wide clefts in the earth. Fine dust was carried to a great distance, and spread deeply over the surface. Enormous quantities of ashes and scoria were thrown up in the air, and fell upon the spot where the eruption began. These last accumulating round solid fragments of rock thrust up from below, and being intersected by melted lava not yet erupted, formed at length a large and lofty hill which has remained to this day with very little change. After all this came forth the lava-current, a semi-fluid mass of solid crystals buried in a tenacious glassy paste, oozing out from the Lava, however, has been known to descend short distances on a slope of 25' at the rate of three feet per second. clefts and crevices produced by the pressure upwards of the pent-up steam and gases, and thus forced above the surface. Unable to accumulate there, the layers of this paste rapidly succeeding one another, spreading over the earth, taking soon a definite direction, and lazily pushing themselves along, filling up inequalities, and at length covering and burying villages, cultivated lands, pools, streams, and springs, and terminating only under the sea. Such as it was ten years after the eruption had ceased, this lava-current remains now a great desolate tract of black cinder, exhibiting in every part the history of the event to which it was due, and illustrating one of the great powers of nature. The whole of the country around Etna is the result of a succession of such actions, extending over a part of the tertiary period into modern times. Geologically, Etna is not old, although there is no evidence to show the exact date of its earliest eruptions. They probably began with little, and have become greater as the mass of erupted matter increased. It is, however, remarkable, that of all the many cones and craters with which the surface is covered, the great central crater of Etna is that which still communicates most directly with the interior exhibiting this by the emission of constant vapour and gases' The numerous subordinate and lower craters, once so noisy and. active, have long since been choked up, but this remains. There have been many eruptions of ashes and lava from the principal crater within the last hundred years, though the chief lava-currents have come from fissures at a much lower part of the mountain. My object in this notice has not been to reproduce the accounts of the eruption of 1669, which are well known to geologists and are easily accessible. I have wished rather to show that the student of geology at the present day may still learn from indications of the event yet remaining a number of valuable lessons. A comparison of this eruption and its attendant phenomena, with the smaller, but not unimportant eruption of Etna that took place last year, made by an eye-witness of the present state of the mountain, may be interesting to the readers of the INTELLECTUAL OBSERVER, and I hope to be able at another time to communicate the results of my visit to the other side of Etna. PRE-HISTORIC MAN IN FRANCE.* AMONGST the recent losses to science which have been occasioned by death, that of Mr. Henry Christy was, from his early age and talent, one of the most deplorable. He rendered distinguished services to geology and archæology by the zeal and liberality with which he conducted and promoted researches in the valley of the Dordogne; and as the preface to the first part of the Reliquice Aquitanica states "he was carried off in the midst of his self-imposed and well-directed work, by acute illness, brought on by over exertion in a visit to the Belgian bone caves, not long after the first few sheets of this book had been put into the printer's hand." We are further informed that he had arranged its style and mode of publication. Many of the plates had been drawn and lithographed in Paris under his and M. Lartet's superintendence, and of some he had prepared descriptions. Upon M. Lartet devolves the task of completing this splendid work, which will be edited by Professor Rupert Jones. "Mr. Henry Christy's executors, desirous of fully carrying out the last wishes of their brother, are resolved to give every assistance in producing the book in the style he contemplated." Every reader must feel a tinge of sadness at the in memoriam character thus given to a work which it was hoped Mr. Christy, as well as M. Lartet, would have lived to finish, and to enjoy that honourable recompense of praise which awaited its publication. The determination of Mr. Christy's executors to carry out his design will meet with general sympathy, and we congratulate them on the issue of the first part, which is produced with as much beauty of type, paper, and illustration as the most ardent admirer of their brother could desire. After some preliminary observations, the work begins with a description of the physical features of the Dordogne district. It is now accessible by the rail from Paris, through Orleans, Limoges, and Périgueux. "After passing the last-named town about eighteen miles, and descending the valley of the Vèezre, between the stations of Miremont and Les Eyzies, the eye is struck," say the writers, " by the sudden change which affects the physical aspects of the country. The two sides of the valley rise in great escarpments of massive rock, more or less interrupted by ancient falls. Their summit is usually crowned by projecting cornices, below which are great horizontal niches or hollow flutings." These curious" flutings" are exhibited * Reliquiæ Aquitanice; being contributions to the Archæology and Palæontology of Périgord, and the adjoining Provinces of Southern France. By Edouard Lartet and Henry Christy. Baillière. on both sides of the valley, and at first sight suggest the idea that they are lines of erosion resulting from strong waterstreams. They are, however, traced to the tendency of the fluted beds to scale off under the influence of weather changes. In the valley thus bounded are numerous caves and recesses, as is common in calcareous formations, and remains still exist of the Rock of Tayac, a mediæval fortress hollowed out of the rock, and which sustained more than one siege. The caves examined by MM. Lartet and Christy are situated in the United Communes of Les Eyzies and Tayac, and in the adjacent communes of Tarzac and Peyzac. The remains of human industry discovered in these caves are not uniform in character, "although within the chronological division of simply worked stone, without the accompaniment of domestic animals." Thus at Laugerie Haute worked flints, like lance-heads were comparatively abundant, but there there were no implements of reindeer horn, though the latter were "found in great numbers at Laugerie Basse, at La Madeleine, and at Les Eyzies, where scarcely any of the flint lance-heads have been met with." Sculptured figures of animals have as yet only been found at three stations-Les Eyzies, Laugerie Basse, and La Madeleine. The cave of Moustier yielded worked flints of a special type, and others like those common at St. Acheul and Abbeville, but no worked bone or sculptured animal figure. "Nevertheless the fauna of the several stations appears to be almost the same, only at Moustier the reindeer is less dominant numerically than at the two Langeries, at La Madeleine, and at Les Eyzies." Separate plates of the molar tusk of the elephant (elephas primigenius) have been found at all the five stations; worked ivory has been met with at Les Eyzies and La Madeleine, and at Laugerie Basse a portion of the pelvis of an elephant. No bone of a domestic animal has been found in either of the five stations mentioned, neither have any of the stone implements an artificial polish. "These two circumstances," say the writers, "suffice to distinguish definitely this first period of the age of stone simply worked, from the second period, when polished stone comes before us, together with domestic animals and habits of agriculture quite unknown to the earlier natives." In a note it is suggested that the men of the first period may not have been ignorant of the art of polishing stones, although they did not polish their implements. Between the two periods, MM. Lartet and Christy consider a great lapse of time must have occurred to account for the disappearance of the reindeer, of which no traces occur in the lake dwellings of Switzerland, or in caves of the same age. In certain cases the animal remains found in the caves may have been transported to them by carnivorous beasts, and in others the supposition of their having been transported thither by floods and torrents may be admissible; but in many cases the presence of works of industry bear testimony to the action of man. The Reliquiæ Aquitanicæ are issued in a quarto form, which gives ample space for large illustrations. In the first part we find four plates of stone implements, and two of bone implements. The figures of flints represent the blocks from which the flakes have been struck, and the various forms of the weapons produced by more or less elaborate working. The bone implements figured consist of barbed arrow or spearheads, and pieces of bone sculptured with figures of fish and quadrupeds, and in one instance with a human figure. The drawing of these figures indicates considerable practice in delineating living objects, and the figures are by no means destitute of expression. The human figure occurs on one side of a cylindrical rod, in company with the heads of two animals referred to the bovine genus, two horses' heads, and an object which may be a serpent or an eel. This is a highly curious work of art, and the human figure is not badly outlined, though details of the face are omitted. When costly works like that of MM.Lartet and Christy come before us, we cannot help regretting that our country has not sufficiently advanced in civilization to possess many public libraries likely to purchase it. Rich collectors gladly buy expensive books of this kind, and they ought to be made generally accessible to students by public libraries in every town. |