of the glens of the Highlands that border the Great Caledonian Valley, because the subject has excited the attention of the tourist and the geologist. In several of the glens of Lochaber, but more especially in that of Glen Roy, there are parallel terraces, at various heights, extending on either side, and which present so regular and artificial an appearance as to have been ascribed to human art; and the ancient Highlanders supposed them to be roads formed by their hero Fingal.

The valley of Glen Roy is of an oval form, and is about four miles long, and one or more wide, being bounded on two opposite sides by high mountains. Through the middle of this valley, a river, formed by the confluence of some mountain-streams, flows into the Spean Water.

On each side of this long, hollow, deep valley, which is bounded by dark and lofty mountains, and at a great elevation, three strong lines are seen, parallel to each other and to the horizon; the levels of the opposite ones coinciding precisely with each other and so striking is this symmetrical character, that the observer can with difficulty divest himself of the idea that he is contemplating some cyclopean work of the olden times. A slight examination of the nature of these parallel terraces is, however, sufficient to convince the instructed observer that they are probably the shores of an ancient lake, fed from the neighbouring Alpine regions, which at distant periods became shallower, and at length entirely disappeared, from the erosion of the barrier which formerly confined its waters.* The following explanation of the phenomenon is from a paper by Mr. D. Milne, which corroborates also the opinions of Professor Playfair and Dr. Macculloch :†—

The parallel shelves or terraces of Lochaber consist generally of bared rocks, forming sloping channels or water-courses; and they bear no accumulations of littoral deposits or detritus. They are perfectly horizontal, and are all coincident with some summit-level, so as to admit of the water flowing over that level as over a lip. Thus the uppermost shelf of Glen Gluoy is exactly coincident with the watershed-ridge which divides that glen from Glen Roy; so that

On the Parallel Roads of Lochaber, by David Milne, Esq., Edinburgh New Philosophical Journal, October, 1847.

+ See Dr. Macculloch, on the Parallel Roads of Glen Roy, Geological Transactions, vol. iv. p. 314; also Mr. Darwin, Phil. Trans. 1839, part 1, p. 39.

the waters which stood at that height must have flowed out at the head of Glen Gluoy into Glen Roy. In like manner the uppermost terrace in Glen Roy is coincident with the watershed-ridge dividing Glen Roy from the valley of the Spey: the waters which stood in Glen Roy, at the second level, must therefore have flowed over the head of the glen into Spey Valley. And the middle terrace of Glen Roy coincides with a watershed at the head of Glen Glaster. Ancient river-courses may be traced leading from the different levels of the terraces into the neighbouring glens and valleys of lower levels; and it seems evident that the waters which formed the several terraces flowed out of the glens, and descended by rivercourses into the low countries. Thus the waters which formed the terrace in Glen Gluoy descended nearly thirty feet by flowing into Glen Roy; those of the upper shelf in Glen Roy flowed in like manner into the valley of the Spey; those of the middle terrace were discharged over the head of Glen Glaster down a slope of 212 feet in vertical height into Glen Spean; and the waters that produced the terrace or shelf in Glen Spean issued out of Lake Loggan by the ancient river-course at Mukkul.

It appears, therefore, that barriers originally existed, which pent up the waters at different levels in the glens, and were lowered at intervals; until at length the lakes were dried up, from the waters sinking from the level of the highest shelf to the next; and thus, by successive steps, as the barrier was worn away, the lowermost terrace was at length formed; and ultimately the system of lakes disappeared, from the barrier having been entirely removed.

E. Page 940.-MR. DARWIN, ON THE GALAPAGOS ARCHIPELAGO. -“This archipelago consists of ten principal islands, of which five exceed the others in size. The largest, Albemarle Island, is of an angular form, and 100 miles in length. They are all formed of volcanic rocks; a few fragments of granite, curiously glazed and altered by heat, can scarcely be considered as an exception. Some of the craters surmounting the larger islands are of immense size, and they rise to a height of between three and four thousand feet. Their flanks are studded by innumerable smaller orifices. I scarcely hesitate to affirm, that there must be in the whole archipelago at least two thousand craters: these consist either of lava and scoriæ, or of finely-stratified sandstone-like tuff. Most of the latter are

beautifully symmetrical; they owe their origin to eruptions of volcanic mud without any lava." A small jet of smoke was seen curling from one of the craters in Albemarle, and eruptions are known to have taken place in modern times.

Great parts of the surface of most of the islands are broken fields of black basaltic lava, thrown into the most rugged waves, and crossed by great fissures, and covered by stunted sun-burnt brushwood. But, while the lower parts of the islands are very sterile, the upper regions, at a height of a thousand feet, possess a damp climate and a tolerably luxuriant vegetation. The commonest bush is one of the Euphorbiaceæ, and, with an Acacia and a great oddlooking Cactus, are the only plants that afford any shade. Coarse grass and ferns abound in the upper parts, but no tree-ferns nor any of the Palm family were observed. Large land-tortoises, in prodigious numbers, are the principal animals, and form the staple article of food to the inhabitants, who are nearly all people of colour banished for political crimes from the republic of the Equator.

The rocks on the coast of Albemarle Island abound in great black lizards, between three and four feet long, belonging to two species; one of which is aquatic, and feeds on sea-weeds; the other is terrestrial. 'They are allied to the Iguanidæ (?), and belong to the genus Amblyrhynchus, which is confined to this archipelago. They have long tails, flattened laterally, and all the four feet are partially webbed. Most of the other organic productions are found nowhere else: there is even a dissimilarity in those of the different islands; yet all show a marked relationship with those of America, though separated from that continent by an open space of ocean between 500 and 600 miles in width. Of terrestrial mammals, there is only one that can be considered as indigenous, namely, a mouse; and even this is confined to Chatham Island, the most easterly of the group. Of land-birds, twenty-six species were obtained, and all but one peculiar to these islands. Of the order of reptiles, in addition to the Amblyrhynchi, there are one small species of lizard of a South American genus, one snake, and of marine turtles, or chelonia, more than one species, and two or three of tortoises. No batrachian reptiles, as frogs or toads, were observed. The Amblyrhynchi are very abundant, and the terrestrial species especially in some places; in James's Island their burrows were so numerous, that it was difficult to find a spot free, on which to pitch a tent. The two

species agree in their general structure, and in many of their habits; they have not that rapid movement so characteristic of the genera Lacerta and Iguana. They are both herbivorous, although the kind of vegetation on which they feed is very different; the land-species feed on the succulent Cactus, and the aquatic species on sea-weed. Mr. Bell has given the name to the genus from the shortness of the snout indeed the form of the mouth may almost be compared to that of the tortoise: an adaptation probably referable to their herbivorous appetites. It is very interesting thus to find a wellcharacterized genus, having its marine and terrestrial species, belonging to so confined a portion of the world. The aquatic species is by far the most extraordinary, because it is the only existing lizard which lives on marine vegetable productions. These islands are not so remarkable for the number of the species of reptiles, as for that of the individuals. When we remember the well-beaten paths made by the thousands of huge tortoises, the many turtles,— the great warrens of the terrestrial Amblyrhynchi,—and the groups of the marine species basking on the coast-rocks of every island in this archipelago, we must admit that there is no other quarter of the world where the Order of Reptiles replaces the herbivorous mammalia in so extraordinary a manner. The geologist, on hearing this, will probably refer back his mind to the Secondary epochs, when saurians, some herbivorous, some carnivorous, and of dimensions comparable only with our existing whales, swarmed on the lands and in the seas. It is, therefore, worthy his especial observation, that this archipelago, instead of possessing a humid climate and rank vegetation, cannot be considered otherwise than extremely arid, and, for an equatorial climate, remarkably temperate. The botany is as peculiar as the zoology. Of flowering plants, 185 species were collected, of which 100 are new; that is, previously unknown to the botanist; and 40 cryptogamic species." Notwithstanding the length of this extract, the reader should refer to the original for many highly interesting particulars, and sagacious comments, which are here necessarily omitted.—Mr. Darwin's Journal of a Voyage Round the World, chap. xvii.

ADDENDA.

I. ELEVATION OF THE LAND. From the following statement it appears, that the slow upward movement of the land is in progress in other countries as well as in Scandinavia (see vol. i. p. 115).

"Gradual rising of Newfoundland above the sea.-The whole of the land in and about the neighbourhood of Conception Bay, very probably the whole island, is rising out of the ocean at a rate which promises, at no distant day, materially to affect, if not to render useless, many of the best harbours on the coast. At Port de Grave a series of observations have been made, which undeniably prove the rapid displacement of the sea-level in the vicinity. Several large flat rocks over which schooners might pass some thirty or forty years ago with the greatest facility are now approaching the surface, the waters being scarcely navigable for a skiff. At a place called the Cosh, at the head of Bay Roberts, upwards of a mile from the sea-shore, and at several feet above its level, covered with five or six feet of vegetable mould, there is a perfect beach, the stones being rounded, of a moderate size, and in all respects similar to those now found in the adjacent land washes."-Newfoundland Times, October, 1847.

In Sir Charles Lyell's admirable Lecture, "On the successive Changes of the Temple of Serapis " (delivered before the Royal Institution of Great Britain, March 7, 1856), we find so much valuable information on the subject of the elevation and subsidence of areas of land, that the following abstract (from the Roy. Instit. Notices) will be of great use to the student.

"The Temple of Serapis, near Naples, is, perhaps of all the structures raised by the hands of man, the one which affords most instruction to a geologist. It has not only undergone a wonderful succession of changes in past time, but is still undergoing changes of condition, so that it is ever a matter of fresh interest to learn what may be the present state of the temple, and to speculate on what next may happen to it. This edifice was exhumed in 1750,