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was subsequently authorized to enable it to be taken through Caroor and up the right bank of the Cauvery, to join the Madras Railway at Errode.

The length of rail in course of construction by the eight companies above mentioned is 4,944 miles, of which 3,332 miles were in working order on the 31st March last. The capital estimated to be required for the completion of the several undertakings already sanctioned is 81,000,000l., of which 60,645,000l. has already been expended. The traffic on the principal lines during the years 1865-66 exceeded the most sanguine expectations, and it is clear now that the traffic on them will be enormous, and that for some time to come it will increase in proportion to the means provided for carrying it. The passenger fares are low as compared with European rates, yet it appears that out of the total number of passengers carried, amounting to between thirteen and fourteen millions during the year, 94 per cent. travelled in the third, 4.78 in the second, and only 1.22 travelled in the first class. A sum of about eleven millions sterling has now been paid by the Government as guaranteed interest, over and above the amounts received from the earnings of the railways; and although it will be some time before so large an advance can be recouped, the condition of some of the railways gives reason to hope that, at any rate, a considerable portion will ultimately be repaid. Moreover, the free conveyance of the mails, and the reduction in the expense of transporting troops and stores, will effect a considerable saving, and the indirect gain to the State, arising from the greater security afforded to the country and the impulse given to commerce and agriculture, is incalculable.

Adverting to the probable early completion of the main lines of communication connecting the port of Bombay with the Presidencies of Calcutta and Madras, the North-western Provinces, and the Punjab, it was recommended by the recent select committee of the House of Commons on the subject of East India communications, that in future the mails for India should be conveyed to Bombay alone, and that the separate postal service between England and Madras and Calcutta should be discontinued. By this means a saving of several days would be effected in the communications between those places and this country.

In addition to the foregoing guaranteed railway companies, two companies, named respectively the Indian Branch Railway Company, and the Indian Tramway Company, have been formed for the purpose of constructing light lines of railway without the assistance of a preliminary guarantee from Government.

The Indian Branch Railway Company, in 1863, laid down a line, about 27 miles in length, with a gauge of 4 feet, from Nulhatte, a station on the East Indian Railway, 144 miles from

Calcutta, to Azimgunge, opposite to Moorshedabad; it was opened on the 21st December, and traffic carried on throughout the following year, though not to so great an extent as was anticipated. The same company has also obtained a concession of an important system of railway communication in Oude and Rohilcund, and considerable progress has been made on a section between Cawnpore and Lucknow, in which case the gauge of 5 feet 6 inches has been adopted, as on the main lines.

In the south of India a branch line has been constructed by the Indian Tramway Company, from the Arconum junction on the Madras Railway, to Conjeveram. This line, which is 19 miles in length, was opened on the 1st August, 1865; light rails have been employed, with a gauge of 3 feet 6 inches, and the total cost amounted to about 4,000l. a mile.

A few words, en passant, concerning telegraphic communication in India. In the early part of 1852, the working of an experimental line of electric telegraph between Calcutta and Kedgeree having proved entirely successful, it was determined to construct a complete system of telegraphic lines throughout India, and the aggregate extent of wire now in operation amounts to not less than about 14,000 miles. After an interruption of more than three years, British Burmah was, during 1864, once more connected with Calcutta by the construction of a land line through Arracan, in lieu of the deep-sea cable, which, after a short trial, utterly failed.

In 1858-59, schemes were proposed for establishing telegraphic communication between England and India, both by way of the Red Sea and the Persian Gulf. The line was laid, and messages were actually transmitted by the former route; but after a short period the signals failed, and all attempts to restore the communication for any length of time proved fruitless. Greater success has, however, attended the construction of the alternative, or IndoEuropean line, which, proceeding from Kurrachee in a westerly direction, along the Mekran coast by Gwadur to Bunder Abbas, and thence up the Persian Gulf to Bushire and Fao, at the head of the Gulf, has a total submarine course of nearly 1,500 miles; a land line has also been constructed as far as Gwadur. From Fao the line is conveyed overland to Bussora, and thence across Turkish Arabia to Bagdad, Mosul, and Diarbekir, whence it proceeds through Asia Minor, by Siras, till it joins the European system at Constantinople. The length of the whole line from Kurrachee to Constantinople is about 3,000 miles, one-half of which is submarine. From Bagdad another line has been taken through the heart of Persia to Teheran, and thence southwards to Ispahan, Shiraz, and Bushire.

With regard to the future, whatever may be said in favour of canal navigation in India, the experiments hitherto made in that direction have not been of so decidedly successful a character as to

lead to the supposition that this means of transit will ever be very much extended. Where practicable, river navigation appears to be extensively used, and the success or otherwise of the works at present under construction with the view of opening up the navigation of the Godavery, will probably determine whether or not similar operations shall be carried out on other rivers. There is also no doubt that by the introduction of an improved class of steamers many rivers might successfully be navigated, which contain too small a depth of water for the majority of the vessels hitherto in use; three such steamers, calculated to draw only 12 inches of water, are now in course of construction for the river Godavery. Should they prove successful on that river, it is not unlikely that they will be followed by others on the same plan for employment on various streams hitherto not navigated by steam, and on which only vessels of very shallow draught could be employed. With respect to railways, it is not probable that any very great extension of the present system of high-cost lines will be sanctioned, except where they may appear necessary for political or military purposes, and we look rather to a development of the principle of light railways, which may readily be laid down along existing lines of road, and ultimately perhaps, when the traffic has become sufficient to justify the expense in a commercial sense, they might be completed substantially so as to unite with the existing system of high-speed railways, just as it is customary to make a fair-weather road in the first place, and afterwards complete it, by bridging and metalling, as a first-class road.

IV. ICE MARKS IN NORTH WALES.
(With a Sketch of Glacial Theories and Controversies.)

By ALFRED R. WALLACE, F.R.G.S., F.Z.S., &c.

ONE of the most interesting branches of modern geology, and that on which recent researches have thrown most light, is the inquiry into the exact modes by which the present surface of the earth has been produced. When we see a vertical precipice, a deep chasm, or huge masses of shattered rock, our first impression is to impute these effects to some violent convulsions of nature, such as volcanic eruptions, earthquakes, or floods. It is, however, now generally admitted that such causes have had, for the most part, little if any effect in modifying the surface, except when many times repeated during long periods of time; and it is every day

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becoming more certain that even the grandest and most romantic scenery of mountainous countries has been produced by the slow but long-continued action of those natural causes which we see daily at work, but whose effects during the few years that we can observe them are almost imperceptible. These causes are, the ocean waves, running water, rain and frost; which, if acting for long periods during which subterranean forces are also at work slowly elevating and depressing large tracts of country and to some extent fracturing and loosening the rocky strata, seem capable of producing all the chief features which the surface of the earth now presents in non-volcanic regions.

There are, however, a considerable number of very remarkable phenomena which none of these causes will account for, and which appear to have been overlooked or thought unimportant till about twenty-five years ago, when the celebrated naturalist Agassiz visited this country after having carefully studied the effects of modern glaciers in the Alps. He it was who first showed that they could be all explained to the minutest detail by the hypothesis of a recent "glacial period," during the continuance of which the mountains of Wales, Cumberland, and Scotland were covered with perpetual snow, and sent down glaciers into most of the valleys, and sometimes even into the sea. At first this hypothesis was received with incredulity and derision, since it completely contradicted the almost universal belief of scientific men that the earth had been for ages cooling, and that all preceding epochs had been warmer than the present one; but it very soon worked its way even among the most sceptical inquirers, till at the present day there cannot be found a geologist who denies the reality of the "glacial epoch," or the correctness of that interpretation which explains many peculiar features of our own mountain scenery by the agency of ice.

A great deal has since been written by geologists and physicists on the effects of ice-work, but comparatively little has been given to the general public; and as the subject is at this time again attracting much attention, owing to new applications of the theory which have given rise to much discussion and are greatly stimulating inquiry, and as it requires little or no previous knowledge of geology to understand either its facts or its theory, I have thought that a popular account of such prominent glacial phenomena as are observable in all our chief mountain districts would be acceptable to many readers of this periodical.

We may conveniently consider the chief evidences of a glacial period under the following heads: 1st, The drift; 2nd, Moraines; 3rd, Roches moutonnées'; 4th, Grooved and striated rocks; 5th, Boulders and perched blocks; 6th, Alpine lakes;-and in this order I propose to record the few observations I have made during a month spent near Snowdon and Cader Idris last autumn, incorpo

rating briefly what has been observed elsewhere, and adding some account of the more interesting problems and discussions to which they have given rise.

1st. THE GLACIAL OR NORTHERN DRIFT.-This is a layer of loose materials-gravel, clay, mud, pebbles, and angular stoneswhich is found spread at intervals all over Northern Europe, and is very common in the valleys and upland slopes of North Wales. It is very abundant all round the town of Dolgelly, where it forms undulating slopes, mounds, and hummocks in most of the valleys, filling up the space between the flat alluvial meadows on the river side, and the steep rocky slopes of the adjacent mountains. Wherever this is cut through in making roads or railways, it is seen to be full of blocks of stone, pebbles, and large masses of rock, distributed through it without any order or arrangement, the top, middle, and bottom being alike in composition. From the contour of the surrounding mountains it can be often seen that this deposit is of great though very variable thickness, probably often exceeding a hundred feet, and it certainly covers many hundred square miles of country in North Wales alone. On ascending the mountains it is often found on their less precipitous slopes and in the upland valleys, at more than a thousand feet elevation; and it has even been traced around Snowdon by Professor Ramsay to a height of more than two thousand feet. The materials of which the drift is composed are various. Sometimes the rocks are nearly all those of the surrounding mountains, at other times they are such as must have been brought from a great distance. The geological age of the drift is determined by its overlying all, even the most recent formations, and by its containing occasionally marine shells of an arctic type and of species which are all now living.

Here we have materials of a loose and miscellaneous nature which were deposited in the sea but not by the sea. That the drift was deposited in the sea is proved by the marine shells which have been found in it up to the height of 1,300 feet on some mountains of Carnarvonshire; and we have thus a proof that North Wales was at a very recent epoch sunk to at least that depth beneath the ocean. The presence of the drift itself, however, at a height of more than 2,000 feet, would prove a much greater submergence. That the deposit could not have been made by the sea, is shown by the want of arrangement of the materials and the abundance of large angular fragments of rock. Water always sorts the materials it deposits. The rocks, the pebbles, the shingle, the sand, the mud, are carried different distances, and deposited in different places or in different layers. Water deposits are stratified. Neither can rocks be carried far by water and retain their angles and clean fractured surfaces. They get rounded into boulders or

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