metres, and some few miles inland, impregnated with this hydromineral dust.

As a proof of the greatly-improved mode of manufacture of sulphide of carbon and its very extensive use, M. Contet states that in 1840 the kilo. of rectified sulphide of carbon cost 50 francs (27.). In 1848 M. Deiss manufactured it, and sold it at 8 francs per kilo.; and now it may be had wholesale at 50 centimes the same quantity. As regards the purification, M. Sidot first re-distils the raw product, then shakes the distillate up with mercury until the latter becomes black, and this operation is so long repeated as the metal is affected by the fluid, or rather by any sulphur dissolved in it. Sulphide of carbon thus purified is freed from the foetid odour it generally has, and exhibits a smell of ether. M. Cloeg renders commercial sulphide of carbon inodorous by leaving it for twenty-four hours in contact with half per cent. of its weight of finely-powdered corrosive sublimate, care being taken to shake or stir up this mixture. The mercurial compound combines with the substances which are the cause of the foetid odour of this substance, and an insoluble compound is deposited. The liquid is carefully decanted, and after a little pure inodorous fat has been added, the sulphide is re-distilled by the heat of a water-bath. The sulphide thus obtained exhibits an ethereal odour, and is eminently suitable for the extraction of oils, fats, &c., from various substances, since on evaporation of the purified sulphide these matters are obtained in as fresh and pure a state as if the oils had been obtained by pressure.

M. Coupier has succeeded in obtaining fuchsine without the use of arsenic by the action of hydrochloric acid and iron, in small quantities, upon pure aniline and nitro-toluol, taking care to apply a suitable temperature. Commercial aniline and commercial nitrobenzol also yield the same result; and M. Schützenberger states that having been requested to test the results of this reaction, he has found that the aniline red obtained is identical with that ordinarily made, and declared it to be a salt of rosaniline. The yield is very fair, and somewhat larger than when arsenic is used.

A lengthy memoir on various processes for preserving timber has been published by Dr. Ott. From it we learn that the opinion that carbolic acid and substances containing it are effectual in preserving timber is erroneous. The real preservative action of the tar-oils is due, according to this author, to a greenish fluorescent oil that comes over at the last stage of the distillation. Direct trials with pyren and paranaphthaline do not yield successful results. The question whether tar (coal-tar) contains a sufficient quantity of the fluorescent greenish oil just alluded to, to justify the use of coaltar for preservative purposes, is answered in the negative. The decay of timber, or peculiar transformation which makes it unfit for

practical purposes, seems to be, in most instances, produced by the attack of fungi and lichens. The mouldering of wood is distinct from decay, it being merely a chemical process caused by the action of water with small access of air. None of the processes invented to preserve timber by chemicals are perfect. The most simple and practical method is the old, but, unfortunately, far too slow plan of properly subjecting timber to the action of air and water, as practised in ship-building yards. A propos of the method of preserving wood by impregnation with sulphate of copper, it may be interesting to know that by an order recently issued by M. le Maire de Douai, the bakers of that town have been prohibited from using the wood of old railway sleepers as fuel for their ovens, since many of these sleepers have been impregnated with sulphate of copper, and there is danger that some compound of copper might poison

the bread.

Professor Morton has described the works at New York where oxygen gas is manufactured on the large scale. The works consist of retort-houses, engine-rooms, store-house, pumps for compressing gas in cylinders, and a gas-holder of 26,000 cubic feet capacity. The process is carried on as follows:- About 700 lbs. of manganate of soda are placed in the retort, and heated to the requisite degree; superheated steam from a boiler is then admitted for about ten minutes. Two equivalents of the manganate of soda and two of water react upon each other, the water combines with the soda of the manganate to form a hydrate of soda, the manganic acid is converted into sesquioxide of manganese, containing only half the proportion of oxygen, and the other half of the oxygen passes off in the free state. At the conclusion of this part of the process the steam is shut off, and the superheated air is admitted for about fifteen minutes, whereupon the sesquioxide combines with more oxygen from the air, and is re-converted into manganic acid, which again combines with soda. The retorts in each furnace are charged with 700 lbs. of permanganate of soda, and by the consumption of 2 chaldrons of coke, and with the labour of three men, 25,000 cubic feet of oxygen are made per day. It is now sold at 24d. per cubic foot, compressed in reservoirs up to a pressure of 250 lbs. to the square inch. The gas is of excellent quality, and very pure.

6. ENGINEERING-CIVIL AND MECHANICAL.

Light Railways.-The great question of the day amongst engineers, at the present time, is the construction of light, or narrowgauge railways. The enormous expense which has attended the laying-down of existing lines upon what is styled the "standard" gauge, and their comparative unremunerativeness, have naturally led to the consideration of how the existing want of increased facilities of communication can best be supplied so as to recommend new projects for railway extension to the confidence of capitalists and the public generally. The subject has also obtained increased prominence in consequence of the arrival of a Russian Commission to investigate the means of communication in this country, and who, together with many other foreigners of distinction, and leading English engineers and others, paid a visit last February to the little Festiniog Railway in North Wales. As this line has the narrowest gauge of any existing railway worked by locomotive power, some description of it here may not be inappropriate.

Festiniog Railway.-This line, which is 134 miles in length, extends from Portmadoc to the slate quarries in the neighbourhood of Festiniog. It is slightly under 2 feet in width of gauge, and was originally constructed for horse traction, by which power it was worked until 1863, when the increased traffic necessitated the employment of steam power for that purpose. The line was strengthened and improved, diminutive locomotives were constructed expressly for it, and since 1865 passenger carriages have been attached to each train. The difference in level between the two termini is 700 feet, and the average gradient is 1 in 92. The steepest gradient on the portion now used for passengers is 1 in 79 82, and the steepest on which locomotive engines are employed, 1 in 60. Some of the curves are exceedingly sharp, having radii varying from 2 chains to 4 chains. As the line is a continuous incline from Portmadoc to Festiniog, the locomotive is employed only to draw the trains in one direction; it then returns by itself, and the loaded trains run by gravitation down to Portmadoc-their speed being regulated by breaks. The original capital of the company was 36,0007. Since that outlay was incurred the line has been almost reconstructed; workshops have been erected and rolling stock manufactured out of revenue, bringing up the total cost of the line to about 86,0007. The net profits have amounted to upwards of 30 per cent. on the original capital, and they exceed 12 per cent. on the total outlay of the undertaking.

New Tunnel under the Thames.-The past quarter has witnessed the completion of a tunnel under the river Thames between Tower Hill and Vine Street, Tooley Street. The noticeable feature

of this work is the extreme rapidity, and comparatively trifling cost at which it has been constructed, the time occupied being only one year, and the total expense less than 20,000l., whereas the old Thames Tunnel occupied eighteen years in construction, and cost over half-a-million sterling. This new tunnel consists of a circular driftway, 7 feet 3 inches in diameter, having an inclination from either side towards the centre of the river of 1 in 30. It is approached on each bank by a perpendicular shaft, that on the Middlesex side being 56 feet deep, and that on the Surrey side 52 feet. The lift at either end consists of an iron chamber, to the roof of which a chain is attached, which passes over a pulley at the head of the shaft, and at the other end is fixed to a balance weight, capable of adjustment according to the number of passengers in the lift. The bottom of each shaft communicates with a waiting-room, having seats along the sides. Along the tunnel is laid a railway of 2 feet 6 inches gauge, on which a small omnibus runs, capable of accommodating fourteen passengers at one time. Under the level of the tunnel at the bottom of each shaft there is an engine-room containing a 4-horse power engine for raising and lowering the lifts, and that on the Surrey side is also employed for hauling the omnibus, which is driven by means of an endless steel cord passing round a vertical pulley-wheel at the Surrey end of the tunnel, and a horizontal pulley-wheel placed between the rails at the Middlesex end.

PROCEEDINGS OF SOCIETIES.

Institution of Civil Engineers.-The session of 1870 was inaugurated on the 11th January by an address from the newlyelected President, Mr. Charles Blacker Vignoles, F.R.S. It would be impossible briefly to summarize Mr. Vignoles' speech, which for interest and importance has never been surpassed, and rarely equalled. In reading over this important paper, it appears that no branch of the profession has escaped notice from the time when "in the earlier stages of the human race their first want must have been, as it is now, a supply of water for men and beasts of tribes, whether nomadic or stationary, when no longer within reach of the natural streams or springs; and assuredly," said Mr. Vignoles, "the individual who first dug a well in the desert, and raised water to the surface, by the simple contrivance of pole and bucket, was the first mechanic-the first pre-historic engineer, whose rude invention has nevertheless been followed in all subsequent ages," down to the completion of the Suez Canal, "by cutting across the sandy ligament which has hitherto united Asia and Africa, by which a water communication has been opened, which will never again be closed so long as mercantile prosperity lasts or civilization exists."

"On the Statistics of Railway Expenditure and Income, and their Bearing on Future Railway Policy and Management." A paper on this subject was read before the Institution on 1st February last, by Mr. John Thornhill Harrison. After referring to the income from passengers and goods on the principal lines in the kingdom, the question of the further extension of railways was considered, and it was urged that many lines might be constructed at a cost of from 3000l. to 5000l. per mile, provided the landowners would sell their land for the purpose at the ordinary market value; that the Board of Trade would allow level crossings, and that gradients as steep as 1 in 20 or 1 in 30 were adopted. The subject of expenditure for working the line was next dwelt upon in some detail, and the percentage of net revenue on the total capital expended. Two large funds for investment of capital were also considered the National Debt, which amounted to 750 millions sterling, and gave a return of 261 millions per annum, or 3 per cent., which was a burden on the industry and capital of the country; and the capital expended on railways, which amounted to 500 millions sterling, giving a return of 20 millions, or 4 per cent. per annum; whilst a sum nearly equal to the interest on the National Debt was annually expended in labour and materials.

Society of Engineers.-On 7th February Mr. William Adams, the newly-elected President, inaugurated the session of 1870-71 by an address. After reviewing the progress of the Society, and adverting to the several papers read during the preceding session, he proceeded to make some remarks upon locomotive engineering and the rolling stock of railways, detailing the several improvements that have of late years been introduced, and especially with reference to the application of break-power for bringing trains to a standstill, the two most important improvements for that purpose being the steam-break of M. Le Chatelier, and the friction-wheel break of Mr. John Clark.

South Wales Institute of Engineers.-An important paper has recently been read by Mr. Brogden, before the South Wales Institute of Engineers, "On the Comparative Merits of Large and Small Trams or Wagons for Colliery use." In the course of the discussion that followed it transpired that at a colliery in the Aberdare Valley there had been effected by the introduction of small trams a saving of 1s. 3d. per ton. In getting out 150 tons a day with a large tram fourteen horses were employed at a cost of 47. 12s. 8d., whilst with small trams the same amount of work was done for 17. 11s. 8d., showing a saving of nearly 6d. a ton on that item alone; besides which there was a difference in the price of driving headways, in the cost of rails, sleepers, &c. By the use of small trams there was also a considerable saving in the men called "dusters," and by reducing the headway a saving in "gobbers."