PROGRESS OF INVENTION.

IMPROVEMENT OF DAVY'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 INCRUSTATIONS.-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 up 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

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. A 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 acid 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, depending 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 The recovery of this iron will not only be a means of get

of iron.

ting 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 little 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.

LITERARY NOTICES.

SUN VIEWS OF THE EARTH; OR, THE SEASONS ILLUSTRATED. Comprising Forty-eight Views of the Earth as supposed to be seen from the Sun at different Hours and Seasons. With five enlarged Sun Views of England, and a Diagram representing the Earth's daily motion in her orbit. By Richard A. Proctor, B.A., F.R.A.S., late Scholar of St John's College, Cambridge; and of King's College, London. Author of "Saturn and its System," "The Constellation-Seasons," etc. (Longmans.)-The changes from spring to summer, autumn, and winter, depending on the positions taken up in succession by the earth in its journey round the sun, may be represented by a series of views of the earth as it might be seen from the sun at any point of the journey. The places which the sun looks straight at will receive a full share of light and heat, those which he looks at more slantingly will receive less, and those out of his reach none at all. Mr. Proctor has devised a highly instructive and pleasing set of pictures illustrating these facts, and giving a far better notion of the cause of the seasons than any diagram we have seen. Plate I. gives four coloured views of the earth at the winter solstice (Dec. 21), at 6 a.m., 6 p.m., noon, and midnight; and at a glance it is seen how the northern regions are foreshortened and the polar portions out of the sun's sight. Plate II. has similar views representing the state of things one month later, and so on in succession through spring and summer to a month before the winter solstice, represented in Plate XII. The XIIIth Plate shows on a larger scale the way in which Great Britain, France, Holland, Denmark, etc., are presented to the sun at various periods of the year. We are glad these drawings are published at a very moderate price, because they will, with the help of the explanatory letter-press, be of great use to schools and families, and to teachers who wish to know how these matters may be made most intelligible to their pupils.

We have also received from Messrs. Longman four charts drawn by Mr. Proctor: one of the Zodiac, on which, with the help of an almanack, the paths of the moon and planets may be easily traced; another of Mars representing that planet as seen from the earth at various points of his rotation. Two other charts represent the orbits of Mars, the Earth, Venus, and Mercury; and of Neptune, Uranus, Saturn, and Jupiter. A great deal of astronomical information is compressed in these diagrams, which are well worth attentive study.

HOW TO USE THE BAROMETER, 1868. By the Rev. R. Tyas, M.A. Cantab., F.M.S., Member of the Scottish Meteorological Society. Author of "Favorite Wild Flowers," etc. (Bemrose and Sons.) The author also calls this little book " A Companion to the Weather-glass.' It contains useful information about instruments, and a series of tabular forms to facilitate the registration of meteorological changes. These are very handy, though on a somewhat small scale. The author likewise does a little weather prophecying,

founded upon principles which he does not explain, but which, he asserts, have usually led to correct anticipations. He says, Although we are unable to say positively that there will be rain in any period-say of seven or eight days-yet the probability approximates so nearly to a certainty, that we may reasonably expect rain or fair weather about the times herein stated, and this expectation leads us to watch more carefully the signs of change." Those who buy this little book may amuse themselves by testing the value of these prophecies.

PHOTOGRAPHS OF EMINENT MEDICAL MEN OF ALL COUNTRIES. With brief Analytical Notices of their Works. Edited by Wm. Tindal Robertson, M.D., M.C.P. The Photographic Portraits from Life, by Ernest Edwards, B.A. Cantab. No. 7, Vol. II. (Churchill and Sons.)—The portraits now given of this interesting series are those of Erasmus Wilson, F.R.S., Sir James Bardsley, and Dr. Thomas Hawkes Tanner. They are all good.

CLIMBING THE HILL. A Story for the Household, by the author of "A Trap to Catch a Sunbeam." (Groombridge and Sons.)— A tale by the author of so exquisite a story as A Trap to Catch a Sunbeam," cannot fail to be welcome. The present story relates to a young couple "climbing the hill." It is gracefully told, and being published in a very handsome form, will make an appropriate new year's gift.

RAIN: HOW, WHEN, WHERE, AND WHY IT IS MEASURED. Being a Popular Account of Rainfall Investigations. With Numerous Illustrations. By G. J. Symons, F.M.S. Editor of "British Rainfall," and "Symons' Monthly Meteorological Magazine." (Stanford Simpkin.)—This is the best book on the subject to assist in spreading a knowledge of various matters pertaining to rainfall, the methods of measuring it, and the utility of the process. Some of the tabular matter is especially interesting, such as the "Fluctuations in the Fall of Rain from 1726 to 1865," and the "Approximate mean Annual Depth of Rain at 165 Stations," in which we observe Lincoln, Southwell, and Stamford stand lowest at 20 inches, while the Stye, near Southwaite, in Cumberland, is at the head of the wet places, and shows an average of 165 inches. London stands at 24 inches, being the same as Norwich and Edinburgh. In addition to this information, we want to know the average moisture in the air, as places may have a good deal of rain distributed in heavy showers, and yet be on the average much drier than other spots where the rainfall is less, and the quantity of vapour greater. Mr. Symons points out the necessity of using the hygrometer as well as the rain-guage, and we hope that, in a few years, accurate information on the English climatology will be obtained. We agree with Mr. Symons' suggestion that local authorities should undertake the slight expense required for daily observation and records. Wind should be registered as well as rain and moisture, and so should temperature and atmospheric pressure. Magnetic and electric observations need not be so general, but should be established upon a system at public cost.

THE BOY'S OWN Book. A Complete Encyclopædia of Sports,