(that is, a solution of phosphorus in carbon disulphide) is placed on the filter-paper; the thread is cut and the balloon left to itself. In the course of half a minute or so the explosion ensues. It is necessary to have an excess of hydrogen in the mixture, because exosmose takes place so rapidly that, by the time of ignition, the volume of that gas is sensibly reduced.

6. ENGINEERING-CIVIL AND MECHANICAL.

In our last number we gave, under the above heading, a brief account of narrow-gauge railways, which, during the period therein referred to, had engaged considerable attention both in this country and in Russia. The necessity for improving the means of local transit has, since then, continued to receive the consideration of all most interested in the question; and a " Tramways' Bill" has recently passed through the Legislature, in which provision is made for facilitating the construction and laying of tramways on common roads.

Street Tramways.-Tramways for passenger traffic have for some time past been in operation in New York, Boston, Washington, New Orleans, and they are becoming general in all the more important towns of the United States. Paris, Genoa, Vienna, Copenhagen, and Brussels, have all their tramways for passenger traffic, and they have also, for some years, existed in Liverpool along the Dock sides. Some years since iron rail tramways were introduced into London, but after a short trial they were ordered to be removed in consequence of the obstructions they caused to ordinary vehicles. At the East End of London a granite tramway has been in existence for many years, extending from the western end of the Commercial Road East to the West India Dock; and in a circular by Mr. J. B. Redman, dated in March last, on the subject of Metropolitan Tramways, it is stated that "practically the tramway is in as efficient working a state as it was twenty years back." The late Mr. Walker conducted certain experiments with granite tramways in 1829, which showed that a powerful draught-horse could draw a load equal to 30 tons upon a level, at the rate of four miles an hour; and in his report on the subject he said, "The friction is not more than upon the best constructed edge railways. I consider that the greater size of our wheels, and there being no flange, compensates for the roughness of the stones (from their being newly laid) as compared with an iron railway."

Whilst fully alive to the advantages of tramways for lessening friction, attention has not yet been sufficiently given in this country to the improvement of our macadamized roads by rolling; and now

that steam road-rollers have been brought to such perfection, the operation is much simplified. Road rolling has for more than a quarter of a century been officially applied over the whole extent of the French and Prussian roads, which are kept up under centralized State superintendence, and perhaps one of the strongest arguments in its favour may be given in the words of the surveyor of the roads near Coblentz, in Prussia, who has observed that as "everywhere in Prussia and in France the highways are rolled, if the systems were not good the expense would not be incurred." Space will not admit of our entering further into this subject now; the whole question has recently been very ably and fully discussed by Mr. F. A. Paget, C.E., in a pamphlet entitled 'The Economy of Steam Road-rolling,' to which we would refer our readers for further information on this head.

The recent movement in favour of tramways in London has resulted in the construction, by the Metropolitan Street Tramways Company, of two short lines, together about four miles in length, the one at Brixton and the other between Whitechapel and Bow. The tram adopted by this Company, and which may class, perhaps, as the best in form hitherto introduced for the purpose, consists of an iron groove fixed level with the surface of the paving, on which the flange of the omnibus wheel travels. The lines are double, and between them as well as in the space between the trams, and strips on either side of about 20 inches wide, the ground is paved with granite sets. The plan of the road, which consists of longitudinal wooden sleepers laid upon concrete, admits of the repair of the tramway, by lifting up lengths of tram and sleeper, without breaking up the road beyond the width of the tram (four inches), and a few stones here and there to undo the fastenings.

Single Rail Permanent Way.-Amongst other novelties of recent introduction, and which come under the category of "Tramways," we may mention two projects for single-line rails. The one by Mr. W. J. Addis, of Tannah, near Bombay, has already been put into practice in India, where it is reported to work very favourably. In this case the rail is intended to be laid down either upon any existing line of road, or on roads made especially for the purpose of a tramway. One of the advantages claimed for this kind of line is that ordinary carts may run upon it, the only necessary alteration being the addition of a central wheel, or wheels, according to the length of the vehicle; the additional wheels being attached to the bottom of the platform of the carts, and having a flange on either side to prevent any moving off the rail. These wheels work on a swivel attached to a screw, by means of which the ordinary side-wheels are raised slightly off the road, so that the whole weight of the vehicles rests upon the central rail.

The second single-rail project to which we have referred was

designed by M. J. Larmanjat, and was first carried out by him in a short trial line, constructed between Raincy and Montfermeil in the summer of 1868. According to M. Larmanjat's system, the tramway is constructed with a single central rail, and along a good road this constitutes the whole of the permanent way. The locomotive employed to haul the trains has four wheels, the two driving wheels, placed on either side, resting on the ordinary surface of the road, and a leading and trailing wheel, having grooved peripheries, and which are situated on the centre line of the machine, bearing upon the central rail. The carriages have also four wheels, arranged in a similar manner, but whilst in the engine the greater weight rests on the side driving wheels, in the case of the carriages the adjustment of the springs is such that the chief weight rests upon the wheels running on the central rail, the other wheels merely serving to steady the vehicle.

Wire Tramway.-Another improved method of cheap tramway construction is found in Hodgson's Wire Tramway system, a specimen of which, five miles in length, has recently been constructed in the immediate vicinity of Brighton. One respect in which this differs from other tramway projects is its unfitness for passenger traffic, it being principally applicable for the conveyance of mining produce and goods generally. Hitherto it has mostly been employed by the French beet-root growers to carry the roots from the field to the storehouses. This tramway consists of a strong iron wire, running over rollers supported on posts, having brackets extending on either side. The greatest length to which one rope line is usually applied is five miles, and a succession of such lengths would be required for any greater distance. At each end of the line is placed a horizontal wheel, around which the rope turns, and at one end is placed an engine for giving motion to the wire. The truck employed consists of a kind of shallow box without a lid, suspended from the wire by means of a bent arm, so arranged that the saddle which rests on the wire is immediately over the centre of the truck. The rope being put in motion, these trucks are caused to run upon it, and are carried forward with it. Where a long line is required, suitable arrangements are made by which the trucks run from one wire on to the next, and so on.

MEETINGS OF SOCIETIES.

Institution of Civil Engineers.-Space will not admit of more than a passing remark on the most important papers read at this Institution. On 8th March, Mr. D. M. Fox read a "Description of the Line and Works of the San Paulo Railway in the Empire of Brazil." The line is 88 miles in length, and was constructed at a total aggregate cost of 1,861,6671. It runs over low swampy

ground for the first 133 miles, and then rises to a height of 2500 feet by means of inclined planes of 1 in 10, worked by stationary engines. From this summit, for a distance of 68 miles, the line crosses a succession of short ridges and valleys, with occasional deep cuttings and embankments A description of "The St. Pancras Station and Roof, Midland Railway," was read by Mr. W. H. Barlow on 29th March. As this work has already been noticed in this Journal, we shall not give any further account of it now. "The Maintenance and Renewal of Railway Rolling Stock," by Mr. R. Price Williams, on 12th April, is a most important and interesting paper, but it is so filled with statistics and figures as to render any short abstract impossible. On May 3rd, Mr. George Berkley read a most important paper "On the Strength of Iron and Steel, and on the Design of parts of Structures which consist of those materials." And on 24th May two papers were read, the one by Mr. George Fowler, "On the Relative Safety of different modes of Working Coal," and the other, "On Coal Mining in Deep Workings," by Mr. Emmerson Bainbridge.

Institution of Mechanical Engineers.—At a general meeting of this Institution, held on 28th April, amongst other business a paper was read "On a Steam Road-Roller." This roller was 25 tons weight, and 9 feet wide; it could roll an area of 300 square yards per hour, with a consumption of coal of about 1 cwt. per hour. The adhesion was found sufficient for gradients as steep as 1 in 9.

South Wales Institute of Engineers.-On the 5th May, at the usual general meeting of this Society, held at Newport, Monmouthshire, discussion was resumed on Mr. J. Brogden's paper "On the Comparative Merits of large and small Trams for Colliery Use," and "On Bernard's Coal-Washing Machine." A paper was also read "On the Application of Blast of a High Temperature to Blast Furnaces of moderate Elevation," by Mr. Thomas Whitwell.

The New York Society of Practical Engineers.-A well-timed paper was read on 20th April last by Mr. C. Williams, "On the Old and New Methods of City Transit," in which a history was presented of the various methods from time to time attempted to facilitate locomotion in cities and towns; and the paper wound up with a description of a method of applying compressed air to locomotive purposes.

LITERATURE.

Report on the Maritime Canal connecting the Mediterranean at Port Said with the Red Sea at Suez,' by Captain Richards, R.N., F.R.S., Hydrographer to the Admiralty, and Lieutenant-Coloneĺ Clarke, C.B., R.E., Director of Engineering and Architectural Works, Admiralty. This report has been published by Govern

ment, and coming as it does from officers of such high authority, after a personal inspection of the Canal, it possesses a peculiar national interest not to be found in similar works by independent individuals on the same subject.

"Principles and Construction of Machinery; a Practical Treatise on the Laws of the Transmission of Power, and of the Strength and Proportions of the various Elements of Prime Movers, Mill-work, and Machinery generally; arranged for the use of Students, Engineers, and Practical Mechanics, by Francis Campin, C.E. The aim of the author is stated in the preface to have been "in the first place to explain the fundamental theories of mechanism in the clearest and briefest manner, so as to impress upon the mind general principles, not special cases, and then to show the practical developments of such theories, care being taken to arrange the matter as to try the faculties of the mind as little as possible." This text appears to have been well adhered to, and the result has been the production of a book calculated to prove of great use to the classes for whom it has been written.

7. GEOLOGY AND PALEONTOLOGY.

(Including the Proceedings of the Geological Society and Notices of recent Geological Works.)

IN the Philosophical Transactions '(1869), p. 445, will be found a most valuable contribution to the Fossil Flora of North Greenland, being a description of the plants (collected by Mr. Edward Whymper during the summer of 1867) by Professor Oswald Heer.

The greater part of the fossil plants which have been brought from Arctic regions have come principally from one locality, Atanekerdluk, in (lat. 70° N.) North Greenland. Here, however, they occur in such profusion that we are able, to some extent, to restore the ancient flora, and deduce most important conclusions as to the former condition and climate of this high northern region. The fossil plants brought home by M'Clintock, Inglefield, and Colomb, and deposited in Dublin and London, were found at this locality, also the very rich collection made by Mr. Olrik (formerly Inspector of North Greenland), and now deposited at Copenhagen. These materials were found upon examination to contain 105 species of plants. Of some the leaves, fruits, and seeds were observed, so that an absolute determination of their species was rendered possible; while of others merely the leaves, and of these, at times, only fragments, were discoverable. Of these latter therefore the identifications cannot be considered as final.

*London: Aitchley and Co.