there was a superfice of 6000 square kilometers capable of inundation, embraced between 34° 36′ and 33° 51' N. latitude, and 3° 40′ and 3° 51' E. longitude. In the central portion. the depth below the level of the sea varies from twenty to twenty-seven meters. None of the large and beautiful oases of Souf would be submerged, Debila, the lowest of all, being fifty-eight meters in altitude. In the Oued Rhir the very inconsiderable and valueless oases of Necira and Dendouga would alone be covered.

The fear had been expressed that the invasion by the sea of the Chott Melrir would produce an infiltration, and thus destroy a portion of the wells that fertilize the oases. There being a large number of the wells situated not only in the Souf, but in the region around and in the vicinity of the basin of depression, it was found that they were all, without exception, fed from a stream above the level of the sea.

It was not thought practicable to investigate the frontier of Tunis, and consequently only the western point of the Chott Rharsa could be examined. It was ascertained, however, that this chott was below the level of the Mediterranean, and that it has a decided inclination toward the Gulf of Gabes. It was also found that the deepest basins of the Chott Melrir and of the Chott Rharsa, although united by the Chott Asloudj, had no direct communication at the pres ent time, being cut off by sand downs. The distance, however, between the two basins is but about twenty kilometers, and could be easily opened by a canal. The plan would be to fill the Chott Rharsa, and then unite it to the Chott Melrir by a section, by which the waters, in flowing through, would soon enlarge the passage to the necessary dimensions. The Tunisian and Algerian basins might be inundated successively, the time necessary for filling being notably diminished from the fact that during the first part of the operation the surfaces submitted to evaporation would be reduced by one half.

Captain Roudaire thinks the general problem of an inte rior sea will be solved as soon as the Tunisian portion is thoroughly investigated, its depth and the relief of the Isthmus of Gabes throughout its entire extent being necessary. This question, however, is not likely to remain long undeter mined, as an Italian commission has been taking levels in

that part, and the cost of the work and the possibility, in an economical point of view, of carrying out the stupendous project will be decided. One thing may be considered as fairly settled, although heretofore not of much controversy, namely, the existence of a vast depression capable of being filled with water.

THE SUEZ CANAL.

The recent report published by the Suez Canal Company, bringing up the statistics of the canal to the beginning of April of the current year, is, in more respects than one, an instructive document. It shows that the prediction of those who favored the enterprise from its inception-namely, that its opening would in a few years revolutionize the trade of Europe and the East-has been practically realized in the five years that the canal has been thrown open to traffic. It gives, furthermore, the gratifying intelligence that the success of the canal as a commercial venture is no longer a matter of doubt and uncertainty, but an established fact, while to Americans the document will afford a substantial argument in behalf of the long-deferred interoceanic canal across the American isthmus.

The canal was open to navigation in December, 1869, since which time to April 1, 1875, 5236 vessels made the transit. Of these 4998 were steam-vessels, and but 238 sailing-vessels, the small proportion of the latter being ascribed to the danger and difficulty of navigating the Red Sea; 2863 vessels passed through from the Mediterranean, and 2373 from the Red Sea.

The statistics by years are here with given, the figures denoting a steady increase of business: 1870, 489; 1871, 763; 1872, 1082; 1873, 1173; 1874, 1264. Up to the end of the first quarter of 1875, 455 vessels had made the transit, which gives an average of 1820 for the year. If the totals above given are divided according to the nationality of the vessels. represented, it will appear that Great Britain was represented by 3602 vessels; France, 416; Austria, 303; Italy, 254; Turkey, 131; Holland, 123; Egypt, 100; Germany, 95; Spain, 63; Russia, 36; Portugal, 22; Denmark, 17; Sweden, 15; the United States, 10; Belgium, 9; Greece, 7; Japan, 4; Burmah, 3; and Peru, Tunis, and Zanzibar, each 1.

In 1870 the net tonnage amounted to 436,609 tons, producing for the company a revenue of 5,048,944 francs; in 1874 the tonnage reached 1,631,640 tons, producing a reve nue of 24,748,900 francs.-1 B, July 25, 231.

THE CHANNEL TUNNEL.

The recent meeting of the British Association gave an opportunity for the discussion of this gigantic project, and the current of opinion was for the most part favorable to its feasibility, so far as the geological and engineering problems involved therein are concerned. With regard to the actual undertaking of the work, it appears to be admitted on all hands, in view of its enormous cost, and consequently its doubtful character as a financial venture, that it must be made a national work, and executed under the combined auspices of the English and French governments. The legis lation looking to this mutual division of responsibility has been conceded by both governments involved in the undertaking, and the reports of the joint commission of English and French government officers now engaged in studying the problem will, in all probability, decide the question as to whether the Channel Tunnel is to be a reality. Sir John Hawkshaw, the president of the British Association, and one of the government engineers of the project, in the discussion before that learned body gave the scheme his decided approval.

ELECTRICITY FOR THE Head-light oF LOCOMOTIVES.

A series of experiments has lately been made by the Russian government with reference to the use of electricity for the head-light of locomotives, a battery of forty-eight elements making every thing distinct on the railway track to a distance of over 1300 feet.-6 C, October 29, 1874, 438.

M. TECHNOLOGY.

XEROGRAPHY, A MANIFOLD WRITING AND PRINTING PROCESS.

By the following process, devised by Hansen, it is said that about 100, or even 200, copies of a manuscript may be taken in ten minutes. In manipulation it is similar to that with oiled paper saturated with a pigment, except that in this case the colored paper is placed beneath, with the colored side uppermost, and upon it, instead of writing-paper, a sheet of firm, thin, very dry oiled paper is laid that will take up the color without absorbing it. There may be a pile of five, or even ten, such layers of alternate colored and oiled paper, and when it is written upon with a pencil or stylus, a copy in reverse will be formed on the lower side of each leaf of oiled paper. From each of these about twenty impressions can be taken by placing writing-paper in contact with each one, and subjecting the whole to the pressure of a rolling-machine, then removing the impressions, renewing the writing-paper, and subjecting the whole to somewhat greater pressure than at first; repeating the operation with increased pressure for each impression up to the twentieth. It is only the blue paper that will afford so many impressions, and it must be thin, and the color must be much more finely ground than it is usually found in the trade. The paper on which the impressions are taken must not be rough, nor should it be too smooth, and the first impressions should be made with the least possible pressure. The printing, copying, or even the lithographic press is not well adapted to this work. If only twenty copies are desired, an ordinary pen in writing will answer.-8 C, September 17, 1874, 332.

STAMPING-INK.

An excellent stamping-ink that dries rapidly and is free from grease may be cheaply prepared, according to Müller, by dissolving one part of crystallized so-called red aniline violet in 30 parts of alcohol, and adding 30 parts of glycerine to the solution. This colored liquid is poured upon the cushion and rubbed with a brush.—5 C, XXXVIII., 1874, 271.

A NEW PROCESS OF ENGRAVING ON COPPER.

The Hydrographic Office at Paris has begun a process of engraving on copper which promises by its rapidity and the moderation of its price to be very widely useful. It consists, in substance, first, in covering a plate of copper with a thin shell of adhering silver, upon which is spread a thin layer of colored varnish; second, in drawing thereon, with a dry point, the lines, topography, and lettering, precisely as one engraves with a diamond upon stone; third, in corroding the traces by means of the perchloride of iron.-6 B, LXXVIII, 1535.

SLATE FOR ENGRAVERS.

As a matter of interest to wood-engravers, we note the reported discovery that plates of polished slate may be used in wood-engraving as substitutes for box-wood. It is declared that such engraved plates will furnish over 100,000 impressions without loss of detail; and, further, that they will not warp, and are not affected by either oil or water. The one drawback which they possess, however, is the fact that they are readily scratched; an objection from which even wood is not entirely free.

FRENCH METHOD OF ENGRAVING ON WOOD.

A French method of engraving on wood consists in first covering the block with a layer of gelatin (0.39 grammes to 31 grammes of water) by means of a soft brush. When this coating is dry, it is covered, in the dark, with a solution prepared of (1) red prussiate of potash, 7.80 grammes; water, 62.20 grammes; (2) ammonio-citrate of iron, 9.10 grammes in 62.20 grammes of water. These solutions are mixed and filtered, and the mixture is kept in the dark. After the layer is dry, it is exposed under a negative from ten to twelve minutes, and washed with a soft sponge, when a blue image appears. If thus prepared the coating does not shell off under the graver.-5 A, January, 1875, 98.

GOLD, SILVER, AND BRONZE INKS.

Most of the gold and silver inks on sale are so wanting in brilliancy and fluidity, and retain their stickiness to such an extent after use, that shell-gold and shell-silver are generally