Here, for the present, we are forced to leave the subject, owing to other demands upon our space, but we shall return to it next week. IRON TRADE OF NORTH GERMANY. coal field it is four times that amount. Prussia possesses 258 forges for puddling and rolling bars and finished iron, with an annual production of 400,000 tons, which sells at the works at an average price of £9 10s. The long distance the coal and ore have to travel, together with the active demand for iron, which the country can by no means supply as yet, seem to be the causes of the high prices which rule in the iron trade. This scarcity allows of an active import trade from England, which, in 1868, was reported at 300,000 tons of wrought iron. In the Prussian forges 50,000 people are employed at 254 iron foundries, making fine castings, chiefly hollow ware, to the for producing wrought iron in masses, both for amount of 150,000 tons. The enormous appliances machinery and cannons, are truly marvellous. Many of the works are engaged upon armour and boiler platos, no less than 30 forges being confined to this department, with an average annual yield of 70,000 tons. This ex-gium, and the North of England as the best Abyssinian steel 7-pounder were made with traordinary development is undoubtedly due to models. There is one feature observable in some a view to substituting it for the small the close proximity of the ores of iron to the of these German blast furnaces which, so far as brass mountain howitzer weighing 24cwt, locality of the fuel. Along the banks of the Rhine we know, is not adopted in England; which is for the small cohorn weighing cwt., and for are to be seen open works and pits, whence con- that the charging platform is supported by iron the royal 54-inch mortars, weighing 14cwt. siderable quantities of hydrated oxide of iron, columns, which are made hollow, and utilised to The mountain steel gun weighs 1461b., is brown hematite, sparry iron ore, and red oxide are convey away the waste gases from the furnace In a blast furnace recently-erected in 2ft. 24in. long, has a 3-inch bore, and throws obtained. Even in the upper course of this tourist-head." a single shell of 71b. and a double shell of haunted stream waggons of the brown oxide and Saxony, at Elchirchen, we were specially struck 121b. weight, the latter enclosing a 1lb. In this coal basin, which may be taken to be an of Charleroi; in fact, we heaps of ore appear on the banks, chiefly the right. with the similarity to those in the neighbourhood were afterwards inbursting charge. It was mounted on a extension eastward of the Liege and Achen seams, formed that the furnace was constructed from wrought-iron carriage weighing 2231b., and there are no less than 65 distinct beds, above 20in. plans designed in Belgium. The height of the was fired with 13oz. charges of L.G.R. powder. thick, making an aggregate of 210ft. of coal, and furnace is 56ft.; the height of the boshes The firing was made in the marsh, the line it is calculated that this district can keep up its is much greater than is usual in English furbeing taking at a target at 800 yards. The present output of 8,000,000 tons for 5,000 years to naces, being 17ft. 4in. from the base. The same elevations were ten in number, and ranged come. The towns of Dusseldorf and Elberfeld, care is evident in the thorough admixture of the from 30deg. to 58deg.; five rounds being with their adjacent villages, form the centre of charge as is so marked a feature in the Belgian fired at each elevation. At the third round this busy scene, where all the branches of the coal process; this furnace being supplied with six at 20deg. the projectile fell on its side. At and iron trades are carried on in a most energetic openings at the top for the introduction of ma33deg. the depth of penetration in the soil-manner, to which the water communication of the terials, and for the same reason to render the Ruhr and Rhine in no small degree contributes. working of the furnace more equable and uniform, which is a stiff clay-was 4ft. 6in.; vertical The third great coal field is that of Silesia, lying and thereby promote the gradual and regular depth, 3ft. At the first round at 43deg. the to the east of Saxony. It extends some 50 or 60 settling of the mass in the furnace, the waste penetration was 5ft. 10in.; vertical depth, miles, and produces about a million tons. Here, gases are withdrawn by four openings, then joined 4ft. 3in.; and at the fourth round, penetra- as well as in many parts of Saxony, is found the in one canal, and led off to heat the boilers, and tion, 4ft. 9in.; vertical depth, 3ft. 6in. In brown or Bovey coal. It is estimated to possess the apparatus for hot blast. The blast is delivered two rounds at 46deg. the projectile was un- only one-third the heating power of the best coal, through copper tuyeres, carefully cooled by the steady in flight, and fell on its side. At the but as it lies generally near the surface, and is, circulation of water. These furnaces smelt a rich second round at 52deg. the projectile be- therefore, cheap and plentiful, it forms an impor- class of ore, the hematite and ferric oxides from haved in the same manner as at 46deg. The tant fuel. Various smaller patches of coal field occur the Erzgebirge, as well as refuse from former projectiles were thrown to a great height, 50,000 tons, and near Dresden, from which is ex-furnaces, the apparatus for conveying the matein Saxony-in the Glane Valley, which produces rich slags. As in many of the Belgian blastthe angles of entrance into the earth for the tracted the coal to supply the celebrated smelting rials to the furnace-top consists of a vertical five rounds at 58deg. being 48, 72, 57, 62, and and refining works at Freiburg. The brown coal hoist, drawn up in slides by a wire-rope, after the 58 degrees respectively. often occurs in superficial deposits, and is easily fashion of a pit cage. obtained by open work, in the same manner as peat is dug out on the North of England moors. With this respect to this Bovey coal, the general opinion among the German miners is that it is of very recent origin, in some cases within the historic period. In a pit near Nordhausen, in the kingdom of Hanover, we were shown a portion of "IS [S Coal Contraband of War?" is being asked such compressed peat or Bovey coal, which there seemed sufficient evidence to show had been placed and answered in the columns of several of in the pit as timber 200 years before, but which our contemporaries. Whatever may be the opinion is now, or at least the greater part of it, converted expressed from the judicial view of this question, into a brown anthracite coal, snapping with an it is certain that coal is the secret of a nation's earthy fracture. This instance was held by the mine position and strength in the civilisation of the 19th century; and that, in fact, the victory of to be a conclusive proof that in certain favourable overseers, who pointed out to us the phenomenon, Sadowa was but the outward and visible sign of circumstances wood may be changed into brown the inward development of the coal and iron in- coal in the space of 200 or 300 years. Notwithdustries of Prussia. None believe more thoroughly, standing the rapid development of the metal trades, or quote with more anxiety, than the French, that and the increased consumption for domestic purworld-renowned saying of Sir Robert Peel, "L'Avenir est au pays qui produira le plus de poses, supplanting the use of peat and wood, the supply of coal in Prussia has far outstripped the Houille," and there can be no doubt that the spec-demand. The annual yield was for the whole of tacle of the rapid development of the mineral resources of North Germany has caused France to cast many an uneasy glance across the Rhine. But a few years ago and the coal trade of North Germany was a feeble and sickly affair-in 1840 the produce was a little over 2,000,000 tons, whilst the annual yield at present exceeds 18,000,000 tons. Before proceeding to speak of the Prussian mines on the banks of the Rhine, we must advert to the coal field near the French frontier, and lying to the south-east of the Moselle. Saarbrück bids fair to earn a double fame. Having already given its name to one of the most important German coal fields, it seems likely to acquire less enviable notoriety in connection with the present war. Stretching along the banks of the Saar, tributary of the Moselle, the coal field, like the kindred Belgian district, occupies an immense hollow of the Devonian rocks. The beds run to an enormous depth, exceeding the deepest seams of the Mons basin, according to a statement of M. Von Dechen, who says, " After repeated trials I have found that the lowest strata known in the country of Duttweiller, near Bettingen, north-east of Saarlouis, dip 19,406ft. and 20,656ft. below the level of the sea.' The present yield of these pits is about 4,000,000 tons, most of which, in the absence of any extensive The iron trade is in a very flourishing metallurgical operations in the district, is ex- condition, though, and partly from the same ported across the Rhine, into the north-east of causes, the tendency of the Belgian trade France, and even to Paris. These mines are to favour the formation of large rather than WE shall shortly have the "Ariadne," "Invinworked exclusively by Government; indeed, it is small firms, is here markedly visible. There stated by her Britannic Majesty's Prussian Consul, in a report on that subject, that in various parts of the country from 150 to 200 distinct beds of coal, representing from 300ft. to 350ft. in total thickness, are being worked by the State. Nearly one-half of the Prussian coal supply is derived from the Westphalian coal basin. Spreading for about 50 miles along the rivers Rhine and Ruhr, this district has sprung into almost fabulous activity. The average population of Prussia is 176 to the square mile, while in the basin of the Rhine Germany: In 1862 1863 1864 1865 Tons. 16,903,520 So that now Germany or Prussia-for to-day the wore, from the last report, 2,600,000 tons of iron In some of the outlying places the old German refining forge is still in operation. At Elbingerode, near the Hartz Mountains, there are several. The forge consists of a hearth, gradually sloping towards the lowest point, where the tuyere directs a constant blast from two pairs of bellows worked by a waterwheel. Two or three raw pigs aro placed on the hearth, with their points directed towards the blast tuyere. The fuel employed is charcoal, and when a portion of the ends of the iron pigs is melted off they are pushed further into the fire. Meantime, the workman stirs up the molten mass in the trough of the hearth with an iron rake, and when it has assumed a pasty consistency, indicating the proper point of decarbonisation, the heat is momentarily raised to refuse and form into a ball, technically called a bloom. The bloom is then worked under a hammer of 8 or 9 cwts. The whole process occupies about five hours. To still further refine the iron it is cut into parts, re-heated, and forged-a process known as klumpfrishen. To produce 2cwt. of forged iron, 2 7-10cwt. of pig iron are needed, showing a loss of 26 per cent. The iron so obtained is of first-rate quality, and even answers to the test of being struck, and bent backwards and forwards over the edge of the anvil several times, without showing signs of fracture.-"Mining Journal.” cible," and other available ships commissioned, a d then Englands Navy will be stronger than it ever has been since she has been called the Mistress of the Seas. Army and Navy Gazette." THE Registrar-General places the area of London delphin by less than 2.000 acres. at 77,997 acres, which exceeds the area of PhilaParis has only 7,802 acres, Vienna 3,728 acres, and Berlin 6,253 acres. Birmingham is in excess of the acreage of Paris, having 7,831 acres. Birmingham must bo In visiting some of the more recently erected healthy, for its rate of mortality is 16 per 1,000, the of these furnaces, we were struck with the perfect lowest of any city; the highest is Leeds, 24 in adherence to what are regarded in France, Bel-1,000. THE AMERICAN GATLING MITRAILLEUSE. | operate on a line with the axes and barrels, and T is said by those who have carefully studied are not attached to any part of the gun, but as the gun is made to revolve, they play back and forth OAK TIMBER. species of I the subject that when war is resorted to, it in the cavities in which they work, like a weaver's THERE are not less than 140 many sorts cultivated is practically less destructive to life to employ the most potent and fatal agent in its prosecution. In this view of the case scarcely any modern implement of war can equal the Gatling battery gun, which from its wonderful powers of destruction may be said to take rank as the foremost of philanthropists. The Gatling battery gun gives to the world an entirely new system of firearms. The inventor is an American, says the "American Engineer," and extensive and perfect machinery at Colt's Armory has been put in operation, where the improved guns are made in great perfection, and so constructed that every part will be interchangeable-an advantage of infinite value, as in service any casualty can be at once remedied, and the effectiveness of the battery preserved by supplying new pieces for any which may have become unserviceable. To give the reader an idea of the character of this gun, it may be said that it can be fired, when well manned, from 400 to 500 times per minute. Its main features may be briefly summed as up follows:-First, it has as many locks as there are barrels, and all the locks revolve with the barrels. The locks also have, when the gun is in operation, a reciprocating motion. The forward motion of the locks places the cartridges in the rear ends of the barrels, and closes the breech at the time of each discharge, while the return movement extracts the cartridge shells after they shuttle, performing their functions of loading and firing by their impingement on stationary inclined planes or spiral projecting surfaces. Second, it can be loaded or fired only when the barrels are in motion, that is to say, when the barrels, the inner breech, &c., are being revolved. Third, it may justly be termed a compound machine gun; since the ten barrels, each being furnished with its own loading and firing apparatus, form, as it were, ten guns in one. This is a valuable feature, for in the event of one of the locks or barrels ecoming impaired, the remaining ones can still be used effectively. The gun bears the same relation to ordinary firearms that the printing press does to the pen, or the railway to the stagecoach. It is no exaggeration to say, that this system marks the commencement of a new era in the history of implements of war. It will, no doubt, be the means of revolutionising, in a great degree, the present modes of warfare. A few men furnished with these death-dealing engines will be able to defeat thousands armed with ordinary weapons. It may safely be said that no other gun which can be rapidly fired, has so great a range and accuracy as the larger-sized Gatling guns, which have an effective range of 2,000 to 3,000 yards. THE "Patrie" states that "at the battle of Woerth six mitrailleuses were taken. These engines had been placed at 800 metres from the enemy, and the artillerists who handled them were killed by the hostile marksmen. At 1,000 metres the mitrailleuses only swept a space of a metre and a half to two metres in width: and those in charge have been fired. When the ten-barrel gun is being fired, there are five cartridges at all times in the process of loading and firing, and at the same time, five of the shells, after they have been fired, are in different stages of being extracted. These several operations are continuous when the gun is in operation. In other words, as long as the gun is were still exposed to the enemy's fire. At 2,000 supplied with cartridges (which is done by means metres they did good service; that is to say, they of "feed-cases," in which they are transported) the covered the front of an entire battalion, and themseveral operations of loading, firing, and extract-selves could be touched only by artillery fire. ing the cartridge shells are carried on automati- Another time we shall know better how to employ cally, uniformly, and continuously. The locks | them, and shall turn the lesson to account." and growing in England, botanists and arborists agree that there are principally two varieties, the Durmast oak, and another which is commonly called the old English oak, although both are supposed to be indigenous. In the Durmast oak the acorns grow in clusters close to the twig, and the leaves are set on short leaf stalks, while in the old English oak together, on stalks of from one to two inches in the acorns generally grow singly, or at most two length, and the leaves are closer to the twig without the intervention of any length of leaf stalk. These are the principal distinguishing marks between the two varieties, and it is doubtful whether any other assumed distinction can be relied upon.. There is no doubt as to the comparative inferiority of the Durmast oak, for almost all the English writers on timber have asserted it, and both Buffon and Du Hamel are of their opinion, and give a decided preference to the oak bearing large acorns on separate stalks, over the oak bearing acorns in clusters, which characteristics are just the distinguishing differences that have been particularised as existing between the English and the Durmast oak. In favourable soils the English oak has seldom more than twelve to fifteen concentric layers of alburnum, but in the Durmast oak there are thirty. This proves at once by analogy the infrequently from twenty to twenty-five or even feriority of the Durmast oak, for it is an established fact that the best hardwood timber is that in which the proportion of heartwood to sap is the largest ; besides which, the numerous layers of alburnum form the basis of a proportion which shows the greater age the Durmast timber must attain before it becomes perfect wood. In England the Sussex oak has always been celebrated as being superior to all other, and in France, the oak of Provence being favourable to its growth. enjoys a similar reputation, the soil, in both cases, Still, an oak tree grown in a soil but ill adapted for it, as for instance, a marshy soil, will retain its superiority of species over the inferior timbers, as the willow and the poplar, to which such a soil is less favourable: although in quality it will fall very far short of the standard of perfection for oak timber. In fact, oak grown on such soils will in some measure partake of the qualities of the timber to which such soils are better adapted, and be of more open texture, of softer fibre, and of less durability, than average oak timber. Oaks of slow growth, those for instance from the mountains of Scotland and from Cumberland and Yorkshire, are very hard and durable. From marshy soils the texture is more open and the colour often of a dull red; or the timber has foxey" stains in it, as incipient decay is called. GUIDING AND CONTROLLING THE MOVEMENTS OF TORPEDO BOATS. N ancient times it was usual for a nation into the rivers, or to stretch stout chains across them to check the advance of the enemy's vessels, and in many cases to form a bar round the coasts over which vessels of deep draught were unable to pass; but as the people became more civilised and christianised those simple contrivances were not considered sufficient for the purpose, therefore they took to laying cases in the channels, which cases contained explosive compounds, which could be fired by a time or other fuse. This mode, however, proved very unsatisfactory, for it required sound judgment and a clear head on the part of the party in charge to light the fuse at the proper time for the explosion to occur at the identical moment when the ship was passing over the spot. After years of manipulating and manoeuvring by hundreds of inventors no satisfactory plan was adopted until Captain Harvey proposed to tow the torpedo out to sea by a small tug or gunboat and run her out under the stern or bows of the vessel it was intended to destroy. This mode has been recently adopted by the Government of this country, and Captain Harvey is deputed to take charge of and instruct the crews of the different vessels in the use of the instrument. In all orders of society the brain is constantly at work to suggest and to carry out in a practical way the working of the various plans, whether such plans have a leaning towards benefiting the human race or to destroy it. The subject of the means of destroying life has engaged the attention of the public for the last few weeks, for we hear of breech-loaders of all kinds being invented by the score, each of which is of greater importance than the other, either from the simplicity of the parts, the fewer operations to perform, the loading and discharging, or in some other item. With regard to torpedoes, a most important invention for guiding and controlling the movements of them has just been patented by Colonel Ballard, of the Royal Engineers, which he describes thus: The system of covering ships of war with armour plating gives additional importance to the use of torpedoes. Cannon to carry shot or shell which will penetrate a ship's armour must be of a most unwieldy size and enormous cost, but it is easy and inexpensive to construct a torpedo which will sink the largest ironclad. So long, however, as torpedoes are merely stationary submarine mines, they can only be useful in the narrowest channels, and are liable to many risks of failure, whereas torpedoes made movable at the pleasure of an operator on shore, or on board a steamer, would become very formidable means of annoying an enemy. It is only by the use of movable torpedoes that we can turn the balance in favour of small swift steamers as against bulky ironclads; armour, and the swift movements and quick turnings of a small vessel, although they may enable her to run away from, do not enable her to fight with, a vessel ten times her size. But if, instead of burning our powder on board onr own ship to send forth our missiles with enormous velocity, but rather uncertain aim and effect, we use missiles of small velocity but more certain aim, movable torpedoes in short, to carry our powder to the side or bottom of the enemy's ship, and there explode it, we adopt a method of warfare which is in favour of small nimble steamers. A large vessel is more easily struck by shot than a small vessel, but it can also receive more shots without sinking. A movable torpedo, while it is also more likely to strike a large than a small vessel, would sink both alike. The best method of manoeuvring torpedoes would be by the aid of electricity. There is no difficulty in a person on shore communicating with a boat by means of electric currents sent through a telegraph cable, and if these currents are made to open and shut the valves of a steam or other power steering apparatus on board the boat, her movements would be quite under the control of the operator at the shore end of the cable. To carry this idea into effect for the purpose of obtaining movable torpedoes, we must construct torpedo boats or rams driven by steam or other power, and with a steam or hydraulic steering apparatus. The valves of this steering gear could be opened and shut by electro-magnets, round the coils of which electric currents could be sent through a submarine cable. The cable could be placed in a tank, or wound round a reel on board the torpedo, and run out as the torpedo advanced. It would affect the vessel's motion no more than hauling the log affects the progress of a ship. The cable is not intended to drag astern but to sink, and it does not matter how often the boat recrosses the same course. So long as there remains any cable on the reel, the torpedo boat is free to move in any direction; nothing retards it but the slight friction of the cable running off the reel. In a strong tide way the cable would form a bight, and run out more rapidly, but there would be no additional drag on the boat, except that caused by the reel making a few more revolutions per minute. In less water than 15 or 20 fathoms the cable would fall to the bottom, and could be subsequently recovered. For deep water it might be made of buoyant material, but it would then be much exposed to injury from an enemy. The cable would not com weigh 50lb. The larger torpedoes are made, the more easily they could be guided, so there is no limit to their size, except convenience and expense. The method by which the steam valves would be opened and shut can be easily understood by a reference to fig. 1. E M is an electro-magnet. The "armature " A A is placed at a short distance from the electro-magnet, so that when a current is sent round the wire the armature is strongly attracted, and rising, adheres to the magnet. This armature A A is attached to a lever l lifting the valve rod r. If now an operator send a current through the wire, the magnet instantly attracts the armature, and raises the valve rod; when the current ceases the valve drops. On each side of the cylinder of the steering gear there would be a valve rod moved by an electro-magnet; on the valve rod are the steam and exhaust valves; when the helm is amidships the exhaust valves are open, and the steam valves closed. An electric current sent through the wires of the port or starboard magnet opens the team and closes the exhaust valve, and the helm is put over. The flow of steam can be controlled with great nicety. Although steam is mentioned, the apparatus may be connected with water valves. A valve on the main steam pipe to start or stop the engine would also be controlled by the operator. This valve would only occasionally have to be opened and shut, and for it the following action, as shown in fig. 2, appears suitable. Here the steam cylinder C has a piston which is to be kept on the position shown by the pressure of steam being on each side of it when the boat is going right ahead. The piston has two rods R projecting through the end covers, and leading by cords over rollers to the helm H. Now when it is necessary to turn the boat to the right or left, one of the valves vor v2 is opened by means of the current acting upon the levers through the electro-magnets E M1 or E M2 as would be well understood, the steam passing into the cylinder by the pipes pl p2 to keep it supplied, but when either valve is lifted for the escape of the steam so that the piston can move, it passes out by the pipes el e as the case may be. These valves are double, and as they are lifted the inlet pipes p' and p are shut off accordingly. The torpedo charge would be exploded by a separate wire. The torpedo boat would thus be fitted with four separate electric actions-one for the port steam valve, one for the starboard steam valve, one for the main steam valve, and one for exploding For small torpedoes the weight of a triple wire If he touches the port key he sends the vessel to port, the starboard key to starboard; both pressed down together start or stop the vessel; the third key explodes the torpedo. Many methods might be suggested for working the relay; much would depend on the nature of the service required. These appliances can, of course, be multiplied indefinitely, and the steam can be controlled on board. The ironclads "Warrior 11 or "Achilles might be so fitted with valves and magnets worked through a cable, that, if steam was up and the guns loaded, the crew could go ashore to amuse themselves, while the captain, seated in an arm chair on the beach with a dozen finger keys before him, could pick up the anchor, send the ship on a four or five mile cruise, fire both broadsides, and cast anchor again without the assistance of a single man. A single torpedo manoeuvring under the guns of a ship or a fort at a quarter of a mile range could hardly have its cable cut by the enemy's boats; the cable would be at the bottom of the sea and could not be found and cut in a moment, the enemy's boats being destroyed by the fire of the guns in the meantime. In narrow channels a torpedo starting from the shore, and moving swiftly down with the tide, would not run much risk of having its cable cut before its work. In such places they would certainly be valuable aids to the defence of the passage, and far more to be depended on than stationary torpedoes. An enemy's ship running up a channel known to be provided with stationary torpedoes would be sure to drag it first, and I do not see how this dangerous service of dragging the Channel could be better performed than with a small steamer worked by a cable in the way here proposed and dragging a grapnel astern. A movable torpedo is available at any part of a Channel, and in many cases at least no precautions could enable the enemy to avoid or destroy it. pedoes near a coast; the sloop being merely in-winters immediately preceding. The condition of The most advantageous way of using torpedoes, however, seems to be to have a few of the smallest ironclads that can be built, and let them fight by twos and threes in a squadron, each manoeuvring as many torpedoes as it conveniently can. Against small swift steamers torpedoes would be of little use, but against large vessels, which take time to get under full speed, or to stop or turn, they would be very formidable, especially when two or three torpedoes attack simultaneously from different sides. A large ironclad ship would require half a dozen steam-launches to take care of it in action, if it expected to meet torpedo boats. Torpedo boats, like stationary torpedoes are more intended for use near a coast than at sea; they could be kept in store, and when wanted be worked by cables from shore or be towed into action near a coast. Sea-going ships could only carry a few small ones, and in deep water the cable would have to be made more or less buoyant, and be less easily run out and more easily cut. The machinery of a torpedo boat would be of the most inexpensive kind; all the minutia which render engines expensive would be omitted, small ones could be made without any furnace, hot water at a high pressure sent into the boiler would give steam enough for a few minutes' cruise. The expenditure of a hundred thousand pounds on an assortment of electro-magnetic steering apparatus of various sizes, with cylinders, valves, magnets, and cables complete, would provide a supply sufficient to equip half the steam barges, and steam launches on the Thames as torpedo boats. A steam barge could be fitted up ready to receive the charge of explosive material. Electricity is also available for connecting or shifting the couplings of ordinary machinery, as THE THE STRASBOURG CLOCK. HE great clock at Strasbourg is one of the wonders of the world about which travellers are often apt to romance a little, making it out more wonderful than it really is. But for all this it is an extraordinary piece of mechanism, and its performances entitle it to rank high in the records of horology. All those who pass through Cheapside witness hourly-nay four times an hour-with some degree of wonderment the activity of a set of figures which strike the chimes and the hours outside the house of one of our most enterprising citizens. But these are wonderfully simple operations as compared with those of the celebrated Strasbourg clock, of which the good citizens are justly proud. Before detailing these performances and describing the clock it may be as well to refer to the history of this ingenious piece of mechanism. For torpedoes to be used at ranges for a few will be understood by fig. 3, where the coupling The clock stands in the cathedral, its origin dating hundred yards I would make the cable so strong F is caused to move along the shafts B and C, by as far back as 1352, in which year it was put up that the torpedo could be hauled back if it failed or which the rotation of one of them is communi- under the patronage of Berthold de Buchek, then was in danger. In this one end of the cable would be fastened to a revolving drum (worked by a strap from the engine, if the torpedo was dispatched from alongside a steamer) and wound in when necessary. Boats built expressly for the purpose of serving as torpedoes should be cigar-shaped, or shaped like a shoe with a spiked front, and the charge placed well forward. They would only expose a few square feet above water, openings would be left through a single funnel for the egress of smoke and ingress of air. Instead of firing the charge by cated to the other. The pin i is on the clutch the slot as shown. THE PROBLEM OF THE AGE. Bishop of Strasbourg. Of the artist's name nothing means of a fuse, it might be fired by the force of UNDER this heading we observe in the papers an carolled a cheerful tune, and a cock crowed and the percussion against the ship's side, but this is not so certain a process; the torpedo might also be sunk just before firing the charge, by opening a valve to fill a compartment with water, and would explode with greater effect. It is not necessary, however, that boats should be built expressly for the purpose to use them as torpedoes. If the requisite steering apparatus was ready in store, a few hours would suffice to fit them to the steam launch of a man-of-war, nor would the fittings injure it. For night service an impromptu torpedo boat or fire ship might often be used with effect. The use of movable torpedoes, taken as part of our armament, would lead to a great deal of economy. Take the chance of a first-rate armourclad vessel costing £300,000 to £400,000, with an expensive armament and a crew of 400 men against a small swift iron-clad sloop costing £50,000 or £60,000, with a crew of 40 men, and using tor advertisement announcing the offer of a prize of twenty guineas by the editor of the " Gardener's Magazine" for the best essay on irrigation as applied both to the farm and the garden, and with reference both to the storage of rainfall and the utilisation of sewage. We gladly give publicity to the offer, hoping thereby to augment and sustain the interest which we trust will be evoked by the judicious and spirited conduct of our able borticultural contemporary. It is time, indeed, that the engineer stood at the elbow of the farmer and occasionally gave the gardener also the benefit of practical advice. Ever since the days of drainage dawned we have been drifting into ruinous habits in respect of the employment of water in the cultivation of the land, and in seasons of drought like those of 1868 and 1870 we have had to behold burnt-up fields and unproductive gardens which might have been luxurious and profitable beyond compare had but precautions been taken to store for use when wanted the surplus rainfall of the clapped his wings. In course of time, however, this clock got out of order, and in 1547 its repair was committed to the charge of Dr. Michael Herr, Chretei Herlin, and Nicholas Prugnor, three mathematicians of repute. They died before their work was finished, but it was taken up by Conrad Dasypodius, a pupil of Herlin, and who completed his task in four years. The clock went well until the year of the great revolution, when it struck for the last time. great clock gradually fell into a very dilapidated Nearly fifty years passed, during which time the state. It was then resolved once more to restore it to its former working condition, but this was found to be impossible, as the works were eaten up with rust and verdigris. At length one Schwilgue, an artist and mathematician of Strasbourg, offered to repair, modify, and reinstate the clock, which task, it is recorded, he commenced on June 24, 1836, and finished in four years from that time. It is stated that Schwilgue received an order to around a skeleton mower. We construct a similar clock for a cantonal capital placed therein) by covered approaches, which are BIBLES OR BREECH-LOADERS. The length of the main buildings, on the ground floor at each side, will be 1,100ft., on the upper floor at each side, 600ft. Their width throughout will be 30ft., and the height of the two floors 60ft. The level of such a length of building will be broken each side by four raised pavilions or dwarf towers four of these, on either side of the north and south extremities, will be 35ft. wide, the two centre ones being 65ft. riage it weighed about five tons. The carriage was placed on an inclined slide, consisting of two large side beams connected by cross pieces. The raised end of the platform was supported on heavy beams of wood, and underneath all was a platform very similar to the slide above, and mounted on trucks which ran upon curved iron racers or rails. The appearance of the whole was that of two rightangled triangles of heavy wood with their longest sides uppermost, the triangles being connected by cross beams of wood. Heavy chains were attached to the carriage, led over strong rollers at the highest angles of the apparatus, and then fastened to a counterpoise, weighing six tons. The counterpoise slid down the lower surface of the incline, being held from falling by grooves in which it moved. Some of the friction was saved by small rollers on the upper part of the counterpoise, and because it is well known that to impart sudden motion to a heavy body causes a great shock, unless that body be freely suspended, strong india-rubber springs or buffers were placed where the chain was attached to the carriage, and also where it was fastened to the counterpoise. The apparatus was simple enough, but a glance was enough to show any one at all accustomed to such matters that the strain must be tremendous. To explain simply the difference in general principle between the Moncrieff method of storing up recoil and this one we will give a familiar illustration, putting aside all the practical advantage obtained by the peculiar curve of the Moncrieff elevators or rockers, and all the disadvantage of the friction caused by gun-carriage and counterpoise in the new apparatus having to work in grooves. The ground floor of the building consists of a series of chambers, broken in equal lengths by the varying dimensions of the central portions, the light for which is obtained from large windows in the Suppose that a great weight has to be lifted from east and west sides of the respective buildings, but there can, of course, be no windows in the sides the ground very suddenly and with as little shock which adjoin and continue the present arcade walls. as possible, because it is advisable that your appaThe lower storey will be set aside for the exhibition ratus shall last a long time-two methods are ofof woollen fabrics, manufactures, tools, and ma-fered you. One is a rope simply led over a pulley chinery. The upper floor will be a repetition, on a smaller scale, of a picture gallery of the Exhibition of 1862; the galleries will have no side windows, but will be lighted with a single centre ridge glass roof. The floor will be fireproof, made on the Fox and Barrett principle, of rolled iron girders filled in between with 10in. of concrete, and tiled on the upper surface. Provision is also made in the girders for heating the buildings by means of hot water pipes, and also for ventilation. The galleries, which are to be 30ft. wide by 25ft. high, will be used exclusively for the exhibition of works of art and art-manufactures, such as painting, bronzes, sculpture, porcelain, decorative furniture, jewellery; in fact, every kind of artistic work, whether applied to objects of ornament or domestic use. A length and breadth of the walk. This trellis-work RIVAL GUN-CARRIAGES. at the end of an inclined beam or frame, one end The second plan offered you is to have the weight fastened to one of the ends of a large rocker shaped like a half moon, so that the weighted end is down and the other nearly perpendicular above it. In this case your pull is to be applied to the upper end, and you have only to make the half moon roll on its curved surface. Surely every one must feel at once, even without more knowledge of mechanism than nature has taught him, that in this case the weight will be moved with less strain upon the arms and with no danger of breaking or shifting anything from its place. This is the Moncrieff principle in its broadest features. But to go a step further, and suppose that in the first case you have not only to lift the weight, but to make it slide in a groove so that it must rub against All the strains are evidently increased. the sides. On the other hand, in the second case, suppose that your rocker is not in the form of a half moon, but has the end next the weight rounded off in a sharp curve. It must be felt that the first strain is still further decreased. What the ordinary daily acquaintance with nature teaches, so that experience soon makes men feel what is generally right or wrong, mechanicians can calculate with accuracy, and although in the case of the apparatus tried on Friday the weight had not to be lifted directly but drawn up an inclined plane, so much friction was introduced that it was evident the shock and strain must be terrible. The first fact remarked by the spectators was that the counterpoise did not bring the gun up to the WHEN an invention appears before the world firing position by its own weight, but that the gunwere adopted, and an unusually cordial vote of simplicity, and asks, with surprise, "How is it we purpose. The second was that the height which thanks to Sir Edward closed the harmonious proceedings. THE EXHIBITION BUILDINGS. W ready for never thought of it before?" Such was the case with the Moncrieff carriage, which had cost the inventor ten years to work out. The idea of using the force of recoil to raise another gun, or a weight that might in its turn lift the piece which had raised it, was by no means new. It had been tried THE buildings in which the Exhibition of 1871 many a time and had always failed. But the The will be held have been designed by Lieut.- manner of doing it and the success were new. Colonel Scott, R.E., and are to be of a permanent difficulty of the problem has been brought home to character. Those persons familiar with the Horti- the minds of all by the trial of another apparatus on cultural Gardens know the long ornamental arcades Friday at Woolwich, a sort of rival to that of parallel with the Albert and Exhibition-roads. At Moncrieff. It was built according to an idea of the back of these arcades is a piece of waste ground, some 200ft. wide, extending to the road. On these strips of land the two main exhibition buildings are to be built. At their northern ends, these main buildings will be placed in communication with the conservatory of the Horticultural Gardens, and through it with the new Albert Hall of Arts (the grand promenade of which will be utilised for exhibition purposes, the educational collection being Captain Grant, inventor of the well-known field The gun used for the experiment was a 7-inch the gun rose and fell was small in proportion to the distance it had to move backwards and forwards, so that a shot coming over the parapet and falling at an angle not less than the incline of the platform would have the gun exposed to to it at whatever point in its ascent or descent the piece might be. Then it could not but be observed that there would be no means of loading if the 7-inch were a muzzle-loader, and all our ordnance firing heavy charges are muzzle-loaders. The gun used in the Moncrieff experiments at Shoeburyuess fired charges of 231b. of powder. The cartridge of the breech-loader used on Friday weighed only 11lb. The actual force of recoil was, therefore, much less in Friday's experiments. Yet, in spite of these advantages, the gun only recoiled 2ft. 4in. at the first round, while the How was this, counterpoise moved but 1ft. 3in. since they were fastened together by a chain which could hardly have stretched? This chain had not stretched, but the india-rubber buffers had been |