before expressed of Mr. Page's labours, and add that his volume is well illustrated, and so low in price as to be within the reach of students of very small means-a fact which we consider important. Mr. Page's larger work made its first appearance in 1856, and the demand for a fourth edition, so soon as 1867, shows the welldeserved repute in which it is held. The present edition appears to notice all recent facts of importance. It is well printed and well illustrated.

PROGRESS OF INVENTION.

A NEW HYDRAULIC CEMENT.-Many excellent hydraulic cements are already known. A very simple and effective one has recently been added to the number by M. Lorel. It is merely a basic hydrated oxy-chloride of magnesium, and it is formed by adding a more or less concentrated solution of chloride of magnesium to magnesia. The magnesia may be very conveniently obtained by adding quick-lime to the mother liquor, that is the residue in salt works, which contains chiefly chloride of magnesium; magnesia will precipitate, and is to be calcined. Double chloride of calcium, and magnesium will remain in the liquid; and if chalk or lime are added, an excellent material for hardening common plaster on walls, etc., will be obtained; or the liquid itself may be used for moistening the materials in making the cement. Magnesiam cement is extremely plastic, and forms a substance like marble. It takes colour well, and it has such agglutinative power, that one part of it is capable of uniting twenty parts sand. It is, therefore, expected to constitute a means of rendering building easy, where building materials do not exist.

NEW TUBULATED SYPHON.-The common syphon, though made of glass, cannot it is obvious, be used with corrosive fluids without great inconvenience. A partial remedy, which consists of an accessory tube containing a bulb, has been long employed. The air is drawn by means of this tube from the lower end of the longer leg of the syphon: the necessary vacuum being thus made, the liquid ascends, and soon begins to flow. The bulb in the accessory tube with moderate care, almost prevents the danger of any of the liquid being drawn into the mouth. M. Zaliwski-Mikorski has, however, invented a syphon which is perfectly safe, and very simple; and in which blowing is substituted for suction. In his instrument, the accessory tube is attached to the lower extremity of the shorter leg of the syphon, and, on blowing into it, the liquid will be drawn up, and the syphon filled, provided the place of attachment is not too far from the liquid.

PRINTING ON GLASS.-Very cheap and beautiful products are now obtained by printing on glass; a large amount of the fine effect of stained glass being had for a very small portion of its cost. The inventor, M. De Mothay, uses for colouring matter pigments mixed with a solution of silicate, or silico-borate of potash and lead,

and a solution of resin in turpentine. The printing is effected with rollers, and the colours are vitrified by heat, no distortion taking place.

A NEW ANEMOMETER.-This self-registering instrument, the invention of M. Radan, consists of a pencil moving uniformly down a vertical cylinder, or from the centre to the circumference of a disc, on each of which paper has been placed. If the cylinder, or disc, is stationary, the line drawn on the paper placed on the cylinder will be perpendicular to the circumference of its base; and that on the paper placed on the disc will correspond with one of the radii of the disc. The pencil is connected with a Robinson anemometer in such a way that, when the cups have made a certain number of revolutions, it is lifted from the paper, an interruption being thus produced in the line drawn upon it. And the cylinder, or disc is made moveable on an axis, at the upper end of which is fixed an ordinary weathercock. The paper on the cylinder, or disc, is divided by lines into spaces which correspond with equal portions of time. The interruption, therefore, in the line made by the pencil, corresponding to a given time, will show the velocity of the wind during that time. And the deviations of the pencil-line from a round line will show its direction during any given time.

A NEW CANNON.-It is a matter of great importance that the force produced by the explosion shall be gradually communicated to the projectile. The inertia of the latter renders this necessary; since, though motion may be communicated very rapidly, it still requires a certain time for transmission. A powder may explode with such velocity, as that instead of the projectile being driven forward, the gun shall be burst; such would be the case were any fulminating compound substituted for gunpowder. Among the means used for securing a gradual communication of the explosive force to the ball is a cannon recently invented in America, and which is said to afford excellent results. Instead of the powder being accumulated in one chamber behind the ball, only a portion of it is placed there, the remainder being introduced into lateral chambers in front of the ball, and communicating by openings with the interior of the gun; when the powder has been placed in any one of these chambers, the opening which forms the communication between it and the exterior is closed by a screw. As soon as all have been charged, the piece is ready to be fired; and the instant the ball has passed the opening leading to one of these chambers the intensely heated gases following the ball, enter it, and exploding the powder which it contains, a new impulse is given to the projectile. This takes place after the latter passes each of the chambers; the explosive force of the powder being separated into successive portions and therefore rendered more effective. The explosion being divided there is less danger of the gun bursting; but the complication, and the time required for loading will be found more or less objectionable.

A SELF-REGISTERING MARINER'S COMPASS.-A mariner's compass which is capable of registering the ship's course, and is by no means complicated, has been invented by the Baron Webel-Jarlsberg, a Norwegian nobleman, connected with the marine. A time-piece, is placed

in the upper part of the binnacle, and is so constructed, that every two minutes it lets fall a very small leaden shot. This shot, falling on the moveable card of the compass, is conveyed by a channel to an aperture in the card, in which is fixed a small glass tube, and passing through this tube, it falls into some one of thirty-two radial compartments, into which a small box, which has been placed under the compass, is divided. As the box is immoveable, and the card is moveable, it depends on the course the ship is following, which compartment a given shot shall fall into; and the number of shots found in a given compartment, will show the length of time during which the vessel was steered in the direction corresponding to that division, since each shot answers to a space of two minutes. The contrivance is very ingenious, but, as at present arranged, it has certain defects: it does not tell exactly the length of time during which the vessel was steered in any direction: and at the end of a given period, only the sum of the times during which a given course was held, and not those times themselves can be ascertained. This, however, is not so inconvenient as might at first be supposed.

SIMPLIFICATION OF THE GALVANIC BATTERY.-It has been found by M. Manuelli Giacomo, that sulphate of zinc may be substituted for the sulphate of copper in a Daniel's battery, without lessening the power of the battery. The effects of such a substitution is a considerable saving of expense, since the cost is merely that of the zinc consumed. He found also that a very good galvanic current will be produced, if zinc is substituted for the copper of the battery. In this case, the zinc constitutes both the electro positive and electro negative metal.

NEW APPLICATION OF GELATINE.-The addition of glycerine to gelatine imparts to it new and valuable properties: the mixture solidifies on cooling, without ceasing to be ductile. Common glue mixed with one-fourth glycerine, becomes very similar in properties to caoutchouc, thus it will remove pencil marks from paper: it may, also be used as a varnish.

A NEW PHOTOMETER.-The transparency of the air on the approach of rains, so that distant mountains become more distinctly visible, has long been recognized as an almost certain prognostic of approaching rain. This transparency is usually considered to arise from the presence of watery vapour; but is said to be partially due to the rendering transparent, or precipitation of, organic matter. This is inferred from the fact that the air coming across arid deserts is transparent in dry weather, but the contrary in moist weather, when it has traversed tracts in which the heat rapidly and abundantly developes animal and vegetable life. In a moist atmosphere, the distant mountain is seen more clearly, because the watery vapour contained in the air either renders the germs of vegetables, etc., transparent, or makes them so heavy that they fall to the ground. And as the sanitary condition of the atmosphere is intimately connected with the presence of organic matters in it, an instrument capable of measuring the transparency of the air, and, therefore, of indirectly indicating the amount of organic matters which it contains, becomes of some importance. M. De La Rive has recently constructed an

instrument of this description. It is founded on the fact that the images of two objects, the rays from which traverse portions of air having different degrees of transparency, will be of different brightness; and that, if their brightness is equalized, the amount of adjustment necessary for the purpose will be a measure of the difference of the transparency of the two portions of air through which the rays from them respectively have passed. To secure accuracy of result, the two objects must be seen with the same eye, in the same general direction, and in the same conditions; and the light from other objects must be excluded. M. De La Rive's instrument consists of two tubes, having each an objective at one end, and their other ends attached to a common eye-glass, of which each objective takes up half the field. The optical axes of the two objectives form an angle which may vary from 0° to 29°, at the will of the observer. The rays passing along the principal axis of each objective are made parallel with the axis of the eye-glass by two rotal and successive reflections-the first from a moveable and the second from a fixed prism. The movement of the moveable prism is so connected with that of the moveable tube, that the angle described by the prism is half that described by the tube. Whatever the points towards which the tubes are directed, the images of these points are in juxtaposition in the focus of the eye-glass. The instrument is proved to be properly adjusted by turning it round through 180°, so that the objects are seen the first and second times through different tubes. The images obtained are equalized by the means used with ordinary photometers. This instrument will measure the comparative brightness of two stars, or of different portions of the heavens.

NEW GAUGE FOR STEAM BOILERS.-One of the most frequent causes of steam-boiler explosions, is an insufficient water supply. This arises in some instances from neglect on the part of those in charge, but more usually from the difficulty of ascertaining the water level within the boiler. Many modes of automatic indication of a deficiency of water have been employed, and to a greater or less extent with advantage, but none are sufficiently effective to remove any possibility of accident. An American has, however, devised an apparatus for the purpose which is very simple, and appears to be very reliable. It consists in a tube fixed into the boiler a little below the proper water level, and projecting for some distance outwards, the internal extremity being open, and the outward closed. Around this tube is a casing, and the annular space between it and the tube is filled with water. As long as a proper water level is maintained in the boiler, the tube remains full of the fluid, but as soon as the water in the boiler falls below the opening of the tube, the latter becomes filled with steam or foam, and the water in the annular space around it boiling, steam is generated, and passes into a space prepared for it, where it blows a whistle, and even, if desirable, acts on a lever that opens the safety valve of the boiler and allows the escape of steam. Thus, not only is there notice of danger, but it is considerably diminished, until the proper measures are taken.

UNDULATING RAILWAYS.-The idea of an undulating railway is

not a new one it has long since been proposed to utilise the force generated by descent down one incline for ascent up the next: so that some of the motive power required for propulsion of a train, should be obtained from gravity. An ingenious means of storing up the force of gravity so as to prevent the great variations of velocity which constitute one of the most serious objections to an undulating railway, is being experimented upon in Paris. The engine by which the motive power used for propulsion of the train is furnished, is provided with two heavy fly-wheels, capable of being made to work with or in opposition to the driving wheels. During descent, these fly-wheels, being made to revolve by the driving wheels, cause great retardation, and at the same time store up the power they have thus absorbed. Continuing to revolve with great velocity when it is necessary to ascend, they are so connected with the driving wheels that they cause them to revolve. The train is thus propelled, and at a practically uniform velocity, since from the large amount of matter the fly-wheels contain, they can lose a considerable amount of motion, without their velocity being greatly affected. Some motive power, independent of that obtained from gravity, would, of course, be required to supply the loss of that destroyed by friction, and the resistance of the air; but the amount must be inconsiderable.

PROCEEDINGS OF LEARNED SOCIETIES.

GEOLOGICAL SOCIETY. — Nov. 6.

Warrington Smyth, Esq., President, in the chair.

A. Tylor, Esq., F.L.S., etc., read a paper on the Amiens Gravel. The author referred first to the prevalent views respecting the gravels of the Valley of the Somme, namely, (1) That there are two deposits of distinct age-the upper and the lower valley gravels; (2) That the former of these is the older; (3) That the Valley of the Somme has been excavated to the depth of forty or fifty feet since its deposition; (4) That both gravels contain bones of extinct, animals, and implements of human manufacture, the lower gravels, however, containing the greater number of species of Mollusca, and the upper the greater number of flint implements; and (5) That the height (seventy feet) of the gravels of St. Acheul above the present level of the Somme is much beyond the limit of floods, and that, therefore, they could only have been deposited before the river channel was cut down to its present level. He then pointed out that the general effect of these views is to refer back the remains of man found at St. Acheul to an indefinite date separated from the historical period by an interval during which the valley was excavated.

In former papers Mr. Tylor stated his belief that the upper and lower valley-gravels of the Somme are continuous, and of