THE MONTH: SCIENCE AND ARTS.

The usual holiday quiet has been animated by news of the discovery that the planet Mars has two moons—that a star in the constellation Cygnus is changing into a nebula—that Mr Stanley has made his way down the Congo to the sea—that Sir William Thomson has invented a chemical indicator which when attached to a sounding-line will tell the depth without stopping the ship, and that the ancient obelisk which has been talked about from the beginning of the present century, is at last on its way from Egypt to England. And now the quiet time is over; for colleges, schools, and hospitals have begun their scientific lectures; the learned Societies are resuming their evening meetings and discussions; the Royal Society have given notice that applications for aid from the funds for promotion of science voted by parliament must be sent in before December 31; and soon the men of philosophy and science will be as busy as the men whose talk is of merchandise.

Planetary satellites are a characteristic of our solar system, and now that the able astronomers at Washington have shewn that Mars has two moons, that mythological deity ceases to be exceptional. Neither in rate of motion nor in distance from the planet is there agreement between the two; for we are informed by Mr Christie of the Greenwich Observatory, that 'the outer satellite revolves once in less than a day and a quarter, and the inner three and a quarter times in one day. The phenomena,' he continues, 'presented to an inhabitant of Mars must be very remarkable, for the outer satellite will remain above the horizon for two and a half days and nights, and the inner will rise in the west and set in the east twice in the course of the night. The lunar method of determining longitudes must be singularly easy with such a rapidly moving satellite, which is equivalent to the addition of a minute-hand to the celestial clock, which in our case has to be read by the hour-hand alone.'

Mr Christie tells us further that the two moons have been seen by observers at Greenwich, Paris, and other places; and he remarks, that if they 'have been in existence for ages, it seems strange they have not been discovered before, especially at the opposition of 1862, when Mars approached the earth as closely as this year; but it is naturally much easier to see an object that has once been found than to discover it independently. The satellites must be much smaller than any of the minor planets hitherto discovered. Can Mars have picked up a couple of very large meteorites, which have approached him closely?'

Leaving this question to the experts, we add, in passing from the subject, that the orbital velocity of one of the moons is seventy-nine miles a minute; of the other, fifty miles; and that their discovery has enabled astronomers to determine the mass of Mars, and thus settle what has been to them an important and long-standing problem.

As a reverse to this astronomical triumph, we have to record the death of Le Verrier, an astronomer pre-eminent among the astronomers of the century, with such insight and such capacity for work as have rarely been equalled. He will be known through coming ages by his theory of the motions of the planets, and the tables founded thereon; for provided with these, astronomers all over the world are enabled to carry on their work with an accuracy hitherto unapproachable, and to widen its application. France has lost one of her greatest sons, and Science one of her most distinguished elaborators; but he lives in his works, and through them will continue to guide and instruct the mariner, the astronomer, and the physicist.

Mr Stanley's exploit in turn settles an interesting geographical question, for embarking on the Lualaba, he followed that river down to the Congo, and the Congo down to the sea. Thus the drainage of the lake-region of Central Africa finds its way into the Atlantic. The voyage proved fatal to some of the party through conflict with hostile natives, and accidents among the cataracts, which on the equator impede navigation for a distance of thirteen miles. The river is described as from two to ten miles wide: it drains an area of one million four hundred thousand square miles; and now with the Congo and the Nile, Africa may claim two of the largest rivers in the world.

It often happens in dark weather that the position of a ship can be ascertained only by sounding; and when near the land, the soundings should be frequent if danger is to be avoided. But as the depth cannot be accurately measured without bringing the ship to a stand-still, the seaman is apt to prefer risk to loss of time; and the consequence is at times—a wreck. Sir William Thomson, to whom navigation is indebted for an important improvement in sounding apparatus, has recently proved by experiment that by adding thereto a chemical appliance the sounding may be taken while the ship is in motion. This appliance consists of a copper tube, attached to the lower end of the sounding wire, and inclosing a slender glass tube, and a small quantity of sulphate of iron. As the tube descends, the pressure of the water forces the sulphate into the glass tube: it leaves a stain on the glass; and according to the height of the stain, as indicated on a scale, such is the depth of the water. We are informed that this ingenious instrument has been tried on board the Minotaur with satisfactory proof of its 'absolute accuracy and extreme handiness.'

H.M.S. Téméraire is appropriately named, for she is big enough and heavy enough to do battle with any antagonist that may venture to face her in the Mediterranean, whither she is bound. The engines are 7697 horse-power. No wonder that the mighty vessel when under way pushes up a ten-foot wave at her bow! The diameter of the principal cylinders is seventy inches; of the crank shaft, twenty-two inches; from which an idea may be formed of the bulk of the ponderous mass. To reduce the weight as much as possible, wrought-iron and brass are largely used in the construction of the engines and fittings, in place of cast-iron, so that in the condensers there are more than eleven thousand brass tubes, which make up a cooling surface of fourteen thousand square feet. To assist the movements and facilitate the working of this giant among war-ships, there are on board thirty-four small engines, thus distributed: two turning, two starting, four feed, two circulating, four fan, two bilge, one capstan, one steering, four pumping, four ashes lifters, two hydraulic gear workers, one torpedo reservoir charger, one to work the electric machine which feeds the lights on the bridge, and four others. In all this there seems something of complication; but we may hope that everything will work well even in the worst of weather, so that the ship may justify her name and the merits of her builders.

The Iron and Steel Institute held their annual meeting at Newcastle-on-Tyne, where, and in the neighbourhood, the manufactures and other mechanical operations abound in which the members take most interest. That these are mines, coking furnaces, brick-works, iron-works, and foundries, may easily be imagined. One of the papers read shewed that cast-steel could be produced without compression, and as readily as cast-iron; which if confirmed by further experiment, will prove of great value in the manufacture of heavy cannon.

In a visit to Sir William Armstrong's works at Elswick, the members saw the welding of coils for guns under the great steam-hammer, which weighs thirty tons, and falls upon an anvil of one hundred and twenty tons, with a stroke of twelve feet six inches; and yet so perfect is the hydraulic moving machinery, that it can be easily worked by one man. The four cranes too by which the ponderous masses of red-hot metal are lifted, are 'under the command of one man, who can sling them right and left, or move the load up or down just as he pleases without moving from his post.' Another example of what can be done by water was shewn at the swing-bridge across the Tyne, which has four spans of about one hundred feet each. The portion which opens weighs fifteen hundred tons. 'The hydraulic machinery for actuating it, is contained in the hollow pier which forms the pivot on which it turns. The pier is surmounted by a watch-tower, in which are the levers for opening and shutting the bridge. It takes just one minute to swing the bridge from its closed position across the river to the open one in line with the stream.'

Mechanists have pointed out that water-engines use the same amount of water when merely driving themselves (which is next to doing nothing) as when exerting their entire power. If it be true that there should be a proportion between the amount of work and the quantity of water, this, as we are informed, is provided for by Hastie and Company of Greenock in an invention by means of which an automatic lengthening or shortening of the stroke of the engine takes place, in accordance with the work to be done. No sooner does the engine become, so to speak, aware of the demand on its power, than it immediately adapts itself thereto without external assistance.

To revert to the Institute: A description was given of the coking coal-field of South Durham; it is thirteen miles long by eleven miles wide, and assists in supplying the present demand for fourteen and a half million tons of coke yearly. At one of the collieries there used to be a waste of three hundred tons of coal every week; but now by means of improved coking ovens, and intercepting the waste heat, this loss is prevented. It is found too that the large deposits of inferior coal can be utilised, by crushing, washing, and then coking: a very important fact, for there is in all our coal-fields a large breadth of coal which has been hitherto rejected as worthless, but which will now be worked and converted into coke.

A paper was read which shews that ways are opening for the utilisation of slag: it is now converted into bricks, cement, mortar, concrete, glass, and cotton or wool. This wool is an excellent material for covering boilers and pipes to prevent waste of heat. Four million bricks have been made, which looks promising.

The Journal of the Institute contains descriptions of machinery with which we may fitly supplement the foregoing: At Smethwick near Birmingham, there is a screw-factory which, with its clever mechanical contrivances, is something to wonder at. All the sizes of screws used in carpentry and cabinet-making are made of iron wire chopped into lengths, and shaped in a series of self-acting machines. A blow on one end forms a head, which is speedily turned true in a revolving chuck, the nick is cut by a small circular saw, a revolving jaw then seizes the head, and the 'worm' or screw is turned in a twinkling; and in this way half a million screws an hour are produced. This seems almost incredible; but the screwing-shed alone covers nearly an acre and a half, and contains two thousand machines. These being self-acting, five or six can be kept going by one woman.

Another example from the same source shews the application of machinery to soft goods and tailoring: At a wholesale clothing establishment in Leeds, more than a thousand hands and three hundred sewing-machines are employed. The cutting-out is done by means of knife-machines driven by steam, which cut through thirty-five layers of thick or a hundred and twenty layers of thin cloth at once, the pattern being marked on the topmost piece. The pile, as is stated, is manipulated around the knife-blade, just as a block of wood is moved when being cut by a band-saw. Pressing-machines heated by gas are used in place of the old tailor's goose, and as they are worked by a treadle, the workman's hands are at liberty to guide the heated iron over the seams.

As our readers know, experiments with continuous brakes for railway trains have been made in England and America. We now learn from a published Report that similar experiments have been made in Germany, and that generally preference is given to the Westinghouse brake. All other things being equal, that must be the best brake which will stop a train within the shortest distance, and that this is done by the Westinghouse appears to be clearly established. This brake has been adopted for the state railways by the Belgian government; and that the question should be settled without delay is regarded as essential in all the countries where it has been tried. The Board of Trade in a recent Report take an unusually decided tone on this point. As the Times remarks: 'They not only constantly refer to continuous brakes as the great railway want of the day, but they also lay down, for the first time, the qualities which a continuous brake ought to possess. The chief of these are instantaneous action when applied either by driver or guard, automatic action, regular use in daily work, and uniformity upon different lines, so that when vehicles from one line are connected with the trains of another the same brake-power may be available for both.' We are further informed that the Board have sent a circular to the railway companies with intimation that the sooner the requirements implied in the foregoing description are put into practice the better will it be for all concerned. There is common-sense in this: it will be read with satisfaction by all who travel by railway.

Social Science this year ventured into a high latitude, and held its Congress at Aberdeen, where the usual endeavours were made to promote health, wealth, and morality, which includes law. A paper read by Mr Caird on 'Economy and Trade,' chiefly as regards agriculture, will comfort those timid folk who are always looking for that troublous time when all our foreign supply of 'bread-stuffs' shall be cut off. 'We grow at present,' he said, 'nearly one million acres less wheat than we did twenty years ago. We have only to revert to the acreage of 1856 to meet such a deficiency as would be caused by all Europe being shut against us. And beyond that, we possess in our immense breadth of pasture-land a never-failing resource of stored-up agricultural power, which could be at once applied to the production of corn, if from any circumstance that course became at the same time necessary and profitable.'

Mr Edwin Chadwick, a veteran among sanitary reformers, read papers on Cleanliness and Health and on 'House Accommodation,' which deserve wide diffusion and careful consideration. But it may be said of these, as well as of many other topics brought forward for discussion, that 'it is better to be in possession of a few important principles than a host of facts; then reflection and reason have elbow-room, and are not hampered and brought to a dead-lock, by cramming a disorganised mass of knowledge into the brain.'

Mr H. C. Russell, government astronomer for New South Wales, has published a descriptive, historical, and tabular account of the climate of that colony in an octavo volume of more than two hundred pages, with a map and diagrams. Although the colony is not yet a hundred years old, Mr Russell has been unable to fill up the gaps which unfortunately exist in the record of its winds and weather; but his book is interesting and valuable nevertheless. He discusses the whole range of meteorological phenomena; he tells us about the hot winds and where they come from; about thunder and hail-storms; about lakes, floods, and tides; about droughts; about the rains, and why they vary; and about the great swarms of moths which at times come in clouds and infest miles of country. In his description of the physical characteristics of New South Wales, he gives particulars which will be quite new and perhaps surprising to many readers. 'Within the colony,' he says, 'may be found all climates, from the cold of Kiandra, where the thermometer sometimes falls eight degrees below zero, and frost and snow hold everything in wintry bonds for months at a stretch, and where upwards of eight feet of snow sometimes falls in a single month, to the more than tropical heat and extreme dryness of our inland plains, where frost is never seen, and the thermometer in summer often for days together reads from one hundred to one hundred and sixteen degrees, and sometimes in hot winds reaches one hundred and thirty degrees, and where the average annual rainfall is only twelve to thirteen inches, and sometimes nil for a whole year.' Clearly there is more scope than was thought for settlers who like 'bracing weather.' In discussing the observations, Mr Russell is of opinion that a periodicity, or a tendency to cycles of phenomena, is discoverable.

How to prevent famine, will be for some time to come a very serious question in India; and while charity seeks to palliate the misery, science is trying to discover the laws of the rainfall, and to devise means of storing large supplies of water against seasons of drought. Examples are not wanting. More than a thousand years ago one of the kings of Ceylon erected a tank, Kanthalai, on a scale so enormous, that were it to be built now it would cost a million sterling. This tank is to be repaired and made available for irrigation. In another district the tank of Kalowewa was twelve miles long and thirty miles in circumference, inclosed by embankments sixty feet in height, and was kept full by two rivers which flowed into it from the hills. In the district of Manaar the Giant's tank offers a further resource, and makes us aware of the pains taken by the natives to secure a sufficient water-supply in former ages. If India has not tanks enough for her wants, they must be built, for periodical famines are an opprobrium to Christian civilisation.

As regards Ceylon, we learn from an address delivered by Sir W. H. Gregory, the governor, that great improvements have been made in that fertile island: jungle and swamp have been converted into rice-fields or lakes: in Kandy there is a constant water-supply: fountains are set up in the villages: laws are in force for preservation of the forests, of the deer, buffalo, and elephant: the pearl-oyster, after some years' disappearance, has returned to the shores: a breakwater is in course of building which will convert the open roadstead of Colombo into a safe harbour, accessible to large ships at all seasons, and it is thought that in time Ceylon will become the great free port of the East.

Pitury is a stimulant said to be of marvellous power, and known to be used by the aborigines of Central Australia; but its origin has hitherto remained undiscovered. Last February, however, after vainly endeavouring for many years to obtain a specimen of the plant, Baron Ferdinand von Müller, Director of the Botanical Gardens at Melbourne, succeeded in getting some leaves; and after careful microscopic examination, he has shewn that they are derived from the Duboisia Hopwoodii, which he described in 1861. This bush extends from the Darling River and Barcoo to West Australia, through desert scrubs, but is of exceedingly sparse occurrence anywhere. In fixing the origin of the pitury, a wide field for further inquiry is opened up, inasmuch as a second species of Duboisia, extends in the forest-lands from the neighbourhood of Sydney to near Cape York, and has also been traced in New Caledonia, and more recently in New Guinea. In all probability the latter shares the properties of the former, as Baron von Müller finds that they both have the same burning acrid taste. The natives of Central Australia chew the leaves of the pitury, just as the Peruvians and Chilians masticate those of the coca, to invigorate themselves during their long foot-journeys through the deserts. Baron von Müller is not certain whether the aborigines of all districts in which the pitury grows are really aware of its stimulating power; but those living near the Barcoo travel many days' journey to obtain this, to them, precious foliage, which they always carry about with them, broken into small fragments and tied up in little bags. The blacks use the pitury to excite their courage in warfare, and a large dose has the effect of infuriating them. It is by no means improbable that experiments may shew that by this discovery a new and perhaps important medicinal plant has been gained.