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urns, they are contracted and have a kind of neck instead of the overhanging lip or rim which characterizes so much of the sepulchral pottery of that period. The urns are formed by hand, not on the wheel, like so many of the Romano-British period, and they are, as a rule, perhaps, more firmly fired than the Celtic ones. They are usually of a dark-coloured clay, sometimes nearly black, at other times they are dark brown, and occasionally of a slate or greenish tint produced by surface colouring. The general form of these interesting fictile vessels will be best understood by reference to the accompanying
engraving which exhibits two of the urns from Kingston. One of these will be seen to have projecting knobs or bosses, which have been formed by simply pressing out the pliant clay from the inside with the hand. In other examples these raised bosses take the form of ribs gradually swelling out from the bottom, till, at the top they expand into semi-egg-shaped protuberances. The ornamentation on the urns from these cemeteries usually consist of encircling incised lines in bands or otherwise, and vertical or zig-zag lines arranged in a variety of ways, and not unfrequently the knobs or protuberances of which I have just spoken. Sometimes, also, they present evident attempts at imitation of the Roman egg and tongue ornament. The marked features of the pottery of this period, is the frequency of small punctured or impressed ornaments which are introduced along with the lines or bands with very good effect. These ornaments were evidently produced by the end of a stick cut and notched across in different directions so as to produce crosses and other patterns. In some districts these vessels are ornamented with simple patterns painted upon their surface in white; but so far as my knowledge goes, no examples of this kind have as yet been found in Derbyshire. One or two examples of domestic vessels, though but in fragments, have been found in the cemeteries; but of these just now it will be unnecessary to speak. Those who desire more extended information on the subject of the pottery of the Anglo-Saxons cannot do better than turn to the sixth volume of the INTELLECTUAL OBSERVER, where they will find an admirable paper on the subject from the pen of my friend Thomas Wright, who, along with another valued friend, Charles Roach Smith, was among the first to clear up the mystery which surrounded the remains of the fictile arts of that people.
Having now fulfilled the promise which I made in the opening of this series of papers, that of devoting them to giving a general insight into the modes of construction and the contents of the grave-mounds of Derbyshire, I close my subject with the earnest expression of a hope that the information which I have given, brief though it necessarily is, may be of service to the readers of the INTELLECTUAL OBSERVER, and may enable them to appropriate to their respective ages such remains of the early inhabitants of our country as may come under their notice. In future volumes of THE STUDENT* I hope to give from time to time some short separate papers on matters to which I have so far but passingly alluded.
* See Notice on page 401.
PROGRESS OF INVENTION.
IMPROVEMENT OF Dave's LAMP.- Many improvements of this most valuable apparatus have been invented : one, very recently proposed, consists in the application of an outer cylindrical case, which is made, in part, of glass, and in part, of wire gauze. Both cases have independent fastenings, and therefore are not likely to be opened by any accident, nor, in ordinary circumstances, can they be opened even by design. Experiments made with this lamp have shown that it is much more to be relied upon than the ordinary kind : since it remains perfectly cool, in an atmosphere in which an ordinary Davy's lamp would be very soon heated to redness.
STEAM BOILER İNCRUSTATIONS.— These, a prolific source of steam-boiler explosions, consists of earthy substances, that are bad conductors of heat, and therefore they permit the boiler, notwithstanding the proximity of water, to be unduly heated : the consequence of which is, that the metal of which it consists is burned, and greatly deteriorated in strength, or the earthy coating cracks, and allowing the water to come in contact with the highly heated metal, a vast quantity of steam is suddenly formed, or the water is even decomposed. The steam in one case, and the gas in the other, gives rise to such a pressure as the boiler may be unable to bear. The prevention of incrustration, besides removing a serious source of danger, would have the effect of economising fuel, by leaving the capacity of the metal for transmitting heat to the boiler unimpaired. One method of preventing incrustrations, is the removal of the earthy matters from the water before it is introduced in the boiler ; this is difficult, and from circumstances often impossible. Another method, is to render the earthy matters harmless, by keeping them in a pulverulent state, and suspended in the water. An improvement on this method consists in arranging a number of small thin plates within the boiler, in such a way as that they over-lap, like the tiles on a roof, and form a thin space between themselves and the walls of the boiler. The heat being imparted directly to the water contained in this space, such a circulation is produced, that any deposit of sediment on the boiler is impossible. The sediment is, however, deposited on the plates; but, not being there exposed to a high temperature, it has no tendency to become a compact mass. This arrangement is attended with another advantage—the uniform and comparatively quiet disengagement of the steam : not in the lower part of boiler, but at, or near the surface of the fluid, on account of the presence of a large amount of solid particles thrown np by the circulation caused by the wall of plates.
Caloric EngineS.—Whether steam or heated air is used, it is only the vehicle for transmissions of the heat from the fuel to the working point, to be changed there into motion. Steam has unquestionable advantages : air has, however, persevering and plausible advocates. M. Bourget has recently introduced a modification of the caloric engine which is attracting considerable attention. He heats the air, after it has been condensed, by a system of tubes which are acid
placed in the flue of an ordinary furnace, and after having expanded in the cylinder, and thus actuated the piston, it is transmitted back to the heating tubes, the caloric it still retains being by this means economized. The heating power of the tubes is augmented by filling them with scraps of metal which render them magazines of heat, absorbing it when it would be in excess, on account of connection with the cylinder having being cut off during expansion, and giving it out at other times. I still better engine of this description has been invented by Mr. Wenham. It is remarkable for simplicity, economy, and compactness. The expansion of air driven through a small furnace and a very mild explosion of carbonic oxide, supplies a perfectly safe motive power.
PURIFICATION OF SULPHURIC ACID.-Sulphuric acid, from the mode of its manufacture, is very frequently found to contain nitric acid, which though small in quantity, is difficult of separation, and if unremoved is often very inconvenient. It has been found, that sulphuric
may be completely freed from nitric, so as to afford no indication of its presence, by means of freshly calcined and pulverized wood charcoal, which may be removed by filtration.
PRODUCTION of CALORIC BY MAGNETISM.-It has been ascertained that the rapid rotations of a magnet, or what is more effective, of a compound magnet consisting of several magnetized bars, will afford caloric. The effect is due to the prevention of motion which the magnet tends to produce. The experiment may be made, by placing above the poles of a magnet, which is capable of revolving on a vertical axis with its poles upwards at the rate of fifteen or twenty times a second, a small copper plate of a circular form, and about half a millimetre thick, and putting upon this plate a flat bottomed flask of considerable capacity, and having fixed in its neck, by a cork, a tube in the form of an S with a little water in its lower curve which is within the flask ; the rapid rotations of the magnet heats the air : and this expanding acts on the surface of the water in the tube and causes it to ascend. When a maximum temperature, depen. ding on the velocity of rotation is attained, the water will remain stationary. M. Louis D'Henry, to whom this experiment is due, believes that with a sufficently powerful system of magnets, and a rapid rotation, water in a copper vessel, placed on the copper plate might be made to boil.
New SUBSTITUTE FOR PHOSPHORUS IN THE MANUFACTURE OF LUCIFER MATCHES.—The terrible effects produced by ordinary phosphorus on those who manufacture matches with it, and the obstacles to the introduction generally of amorphorus phosphorus renders a substitute for this pernicious material very desirable. Such a substitute is most probably to be found in a mixture recently discovered by M. Böttger. It consists of eight parts trioxide of thallium, and one part penta-sulphuret of antimony: and may be ignited by friction.
UTILIZATION OF THE RESIDUES OF THE SMELTING FURNACE.—Large quantities of cinders, hitherto incapable of use for any industrial purpose are produced by smelting furnaces. They have been found on examination to consist for the most part of very minute globules of iron. The recovery of this iron will not only be a means of getting rid of very large quantities of very troublesome material, but a source of considerable profit.
NEw MODE OF MANEUVERING A VESSEL.-Floating batteries are being constructed for the protection of the coasts of Sweden. They are provided with a turret: and as the turret does not revolve, in order to secure the power of aiming the gun it contains in all directions, it is necessary that the vessel itself should rapidly turn round. This is effected with ease and certainty, by means of a paddle wheel fixed at the bow, and turning on an axis which is parallel to the length of the vessel. This wheel is entirely immersed and therefore if constructed in the ordinary way with fixed floats, it would produce no motion, the floats on opposite sides neutralzing each other. It is therefore so arranged that the floats, when in a higher position feather, and move through the water horizontally so as to have no effect in producing motion. The floats which are at the time in a lower position produce a maximum effect. This paddle wheel offered litti resistance to the progressive motion of the floating battery as the floats are made of thin sheet iron : and they present their edges to the direction in which the vessel is moved. Such an arrangement would however not be suitable with other than vessels intended to remain constantly at or very near the same place.
PRODUCTION OF DETONATING POWDER, WITH THE MATERIALS OF ORDINARY GUNPOWDER.—It has been found that the rapidity of combustion of gunpowder depends greatly on the nature of the charcoal employed; the development of this fact has been carried so far, by a suitable selection of the charcoal, that the combustion becomes so rapid as to be an explosion of the unconfined powder. This is effected by the use of carbon obtained from rice starch, the albumen of blood, or leather. With nitrate of potash such carbon forms not ordinary gunpowder but a detonating material.