silica, some phosphorus and sulphur. The carbon is hardly at all removed. The appearance of the iron after the process is that of refined metal. The cost of the process is nil, as the iron contained in the hæmatite is reduced, and adheres as cast-iron to the bottom of the iron in the mould. There is no sand or coke-dust used, and the refined iron goes clean into the puddling-furnace. The yield in puddling is that of refined iron, about 21 cwt. to the ton of puddled bars. The puddlers like to have one or two pigs of white iron with the metal so refined, as they say it works more liquory, showing that when the silicon remaining is only 0-200 or 0-300 per cent. the charge does not possess the necessary fluidity. The puddling furnace keeps longer in repair, no other fettling is used than hammerslag, and the former allowance of shearings to make scrap-balls has been discontinued. The men do more regular work, and, like the refined iron, the yields are larger. The puddled iron is of an improved quality, and much liked in the rail mills. A second process is the same in every respect as the first, only that gths by weight, and half by bulk, of nitrate of soda is mixed with the hæmatite ore, which is formed into a paste and applied in the same way. With this mixture the ebullition is greater, the flame is of a yellowish colour, showing the ignition of some of the soda. The cinder is thrown up and out of the iron, over which it forms a crust, which can be separated when cold. The iron has a cellular and honeycombed fracture, like metal much overblown. The scoriæ contain sulphur, phosphorus, silica, and soda. The iron works drier and cleaner, and to a better yield than that made by the first process, but should have about one-third of grey pig added to make a very clean and tough iron. The only cost of the process is the nitrate of soda, which in the proportion named comes to about 4s. a ton at its present high price.

11. PHYSICS.

LIGHT.-The Rev. Father Secchi has published an account of the spectrum of the planet Neptune; he first refers briefly to his former observations of the spectrum exhibited by Uranus, and then states that the spectrum of Neptune consists chiefly of three lines, or bands, placed near the green line, and that its light is entirely devoid of red; this is confirmed by the colour exhibited by the planet when seen through a telescope, which is a sea-green.

M. Bontemps, the managing director of the celebrated crystal glass works of Choisy-le-Roi, states, in his observations on the colouration of glass under the influence of direct sunlight, that he was led to the following results:-Within three months after

having been exposed to sunlight, the best and whitest glass made at St. Gobain is turned very distinctly yellow; extra white glass (of a peculiar mode of manufacture) becomes even more yellow, and gradually assumes a colour known as pelure d'oignon; glass containing 5 per cent. of litharge is also affected, but far less perceptibly; crystal glass, made with carbonate of potassa (the other varieties referred to contain carbonate of soda), litharge, and silica, is not at all affected; English plate-glass, made by the British Plate-Glass Company, and exhibiting a distinctly azure-blue tinge, remains also unaffected. The author attributes this colouration, which begins with yellow and gradually turns to violet, to the oxidizing effects of the sun's rays upon the protoxides of iron and manganese contained in glass.

A solution of iodide of potassium is, even when kept in wellclosed bottles, slowly decomposed by the action of daylight, and assumes a somewhat yellowish tinge due to free iodine. M. Loew filled a number of glass tubes for about from one-half to threefourths of their capacity, with a solution of iodine of potassium, and, after having sealed these tubes, exposed them to direct sunlight. Another set of tubes were likewise filled with the same solution, but all air was expelled, and the tubes sealed during and after the solution had been boiling for a considerable time. These tubes were also exposed to the action of direct sunlight; after three or four months' exposure the tubes and contents were examined, those wherein no air at all was left were found to be perfectly colourless, no decomposition of the contents having taken place. As regards the other tubes, the following results are noticed:-(1) Under the influence of light, the oxygen of the air decomposes iodide of potassium, iodine in small quantity is set free, while hydrate of potassa is found in the liquid. (2) This decomposition is limited, and does not even, when a large quantity of oxygen is present, increase, because a portion of the iodine set free enters again into combination with the caustic potassa set free, forming iodide of potassium and iodate of potassa. (3) The testing for ozone by means of a solution of iodide of potassium and starch (or paper prepared therewith) is of no value whatever, unless care has been taken to exclude direct sunlight.

HEAT.-M. Dufour recommends the following process for demonstrating that the flame of a candle is formed of a hollow cone, luminous on the outside only, and dark in the interior. A caoutchouc tube has, at one of its extremities, a gas jet with an almost semicircular slit of .04 metre in depth. The other end of the tube communicates with a reservoir of water placed at a convenient height. Upon a suitable pressure, the water flows out by

the slit in the jet, producing a clear sheet. The slit is placed in such a manner that the sheet presents a horizontal surface, and this will easily cut the flame of a candle, showing a perfect section. The hot gases and carbonaceous particles are carried off by the water. On placing the eye above the hollow cone, the luminous wall, &c., can be distinctly seen. Sections may easily be made near the wick or near the point; nothing hinders observation, which may be prolonged at pleasure, and a lens may be used if desired. If a current of air be caused to come out of the slit by bellows, an invisible sheet of air is formed which is also very convenient for making a section of flame. Close observation is quite possible, for the aërial current prevents the heated gases from reaching the eyes, and a lens may be used as in the former case. The flame forms a cone, whose luminous walls are extremely thin, and their size can be plainly seen. A platinum-wire may be introduced across the section; and on being plunged as far as the wick it will remain unreddened in the dark interior of the cone. If a jet of gas produced by a fishtail burner be cut, the luminous fan will be found to consist of two brilliant blades, between which there is a narrow obscure space. The blades are at a greater distance apart, and the dark space is wider towards the end of the fantails; M. Dufour suggests that this method might be of service in the chemical analysis of flames.

Mr. Spence has made public an apparent paradox in the science of heat, whereby he is enabled to raise a higher temperature in certain solutions, by steam of 212° Fahr. He selected a solution of a salt (nitrate of soda) having a high boiling-point-about 250° F. The nitrate of soda was placed in a vessel surrounded by a jacket; steam was let into the intervening space, until a temderature of nearly 212° F. was obtained; the steam was then shut off, and an open pipe immersed in the solution, and steam from the same source was thrown directly into the liquor; in a few seconds the thermometer slowly, but steadily, moved, and minute after minute progressed, until it touched 250° F. This unexpected fact has become to the author of immense practical value. As a corroboration of the theory which seems to explain the apparent paradox, the author finds that the temperatures of his solutions are in the exact ratios of their specific gravities, and have no connection with the temperature of the steam, which never exceeds 212° F.. The greater the specific gravity of his solutions, the higher the boiling-point; and therefore, whatever the boiling-point of the solution in water of any salt, to that point, or nearly, will steam of 212° F. raise it.

The annoyance which arises from the bumping of certain liquids when submitted to distillation or boiling has often attracted the

attention of chemists, and various means have been proposed for its prevention. Dr. Hugo Müller, F.R.S., has described a ready means for overcoming this annoyance. In cases where the introduction of any foreign matter into the liquid about to be distilled is undesirable, he indroduces through the cork in the tubulus of the retort a glass tube, which is drawn out to a long capillary tube, and pressed tightly to the bottom of the retort. The upper end of the glass tube is connected by means of an india-rubber tube, with a generator of carbonic acid or hydrogen, or a gas-holder containing air; and whilst the distillation is going on, one of these gases is passed in a slow but continuous current through the liquid. Under these conditions all bumping is avoided, and the distillation proceeds with the utmost facility. For ordinary purposes, however, it is still more convenient to introduce into the liquid about to be distilled a small fragment of sodium amalgam, or, in cases where the liquid is acid, a small piece of sodium-tin. Methylic alcohol is well known to be one of the most difficult liquids to distil, yet on the introduction of a minute piece of sodium amalgam or sodium tin it can be distilled without the slightest inconvenience. The action of sodium amalgam and sodium-tin is due to a minute but continuous disengagement of hydrogen taking place during the process of distillation.

Dr. Hofmann has described an ingenious experiment to show that a body really increases in weight during combustion. A small horse-shoe magnet is hung up at the beam of a balance, sufficiently sensitive to turn with centigrammes; the poles of the magnet are immersed for a moment in levigated iron, when a beard of small particles of iron adheres to the poles; by means of proper weights placed on the scale-pan at the other end of the beam the equilibrium is restored. This having been done, the finely-divided iron is kindled by approaching to it the flame of a Bunsen gas-burner, and continues to burn. While burning, it will be seen that the arm of the balance on which the magnet is suspended considerably deviates from the horizontal position, thus indicating an increase of weight on the side where the experiment is going on. This experiment succeeds best with a magnet of moderate dimensions. The horseshoe magnet applied in this instance weighed without its armature 210 grms., and can bear a load of 12 5 grms. of iron. When this is altogether converted in magnetic oxide by combustion the increase in weight will be about 4·7 grms.

Dr. Seelhorst has repeated Barrett's well-known experiments of holding in the flame of burning hydrogen gas very well-cleaned glass rods, metals recently cleaned by filing them just previous to the holding in the flame, and has observed the same blue colouration as Mr. Barrett did. But the author is not inclined to ascribe

this colouration to the effect of sulphur, which should be so generally spread about in the shape of some sulphate as to produce this colouration. The author, though abstaining from stating any precise cause at all, inclines to the belief that the cooling effect of the cold body held in the flame has something to do with this phenomenon. Perfectly pure hydrogen, burning from a platinum burner, as well as from iron or glass burners, exhibited the phenomenon, when cold bodies, just after having been cleaned by scraping or filing, were held in that flame.

According to M. Baille the moon's surface emits as much heat as a cube filled with water, covered with lamp-black, having a surface of 6 5 square centims., and placed at a distance of 35 metres from the thermo-electric measuring apparatus employed by the author for his experiments.

In a paper "On the Reflexion of Heat on the Surface of Fluor Spar and other Substances," by M. Magnus, we learn that the following substances reflect at an angle of 45° the undermentioned quantities of heat:-silver, between 83 and 90 per cent.; glass, between 6 and 14 per cent.; rock-salt, between 5 and 12 per cent.; fluor spar, between 6 and 10 per cent. The same author finds that different bodies heated to 150° emit different kinds of heat; some substances only emit one kind of heat, others, again, various kinds. Pure rock-salt is mono-thermic, sylvine (chloride of potassium) behaves in a similar manner.

M. Delaurier proposes for concentrating and utilizing the sun's rays, a truncated cone, open at both ends and lined inside with polished silver, the sun's rays being admitted by the largest opening. Since the angle of reflexion is equal to the angle of incidence, all direct or reflected rays will be united at the narrower end of the cone. It is clear that the greater the length of the cone, the greater will be the concentration of heat. The author enters into a discussion on the advantage of this contrivance over the use of lenses and mirrors, and he very enthusiastically surmises that the heat of the sun's rays may be so concentrated as to serve for various purposes instead of the combustion of fuel, especially in countries. where, as in Algeria, the heat and splendour of the sun are more permanently felt than it is in our climate.

ELECTRICITY. Our limited space prevents us from doing more than allude to one or two novelties in this science. Dr. Runspaden has published a monograph on a subject first observed by Professor Wöhler, that when water acidified with sulphuric acid is decomposed by a galvanic current, and silver is used as electrodes, peroxide of silver is deposited on the anode, and metallic silver on the cathode. The two main questions answered by the author by a series of