of one foot is slightly higher than that of the air, the difference in the summer amounting to about 3o. Dr. van Bebber suggests a new means of weather prediction. Ignoring the vagaries of low-pressure systems, he deals with persistent anticyclones, and defines their laws. On January 12 a cyclone of unusual energy passed over the British Isles, taking forecasters by surprise, and moving at a rate of thirty-four miles an hour. In the north-west of Ireland the force of the wind reached to 12 of the Beaufort scale, which is equivalent to ninety miles an hour, or "that which no canvas can withstand." On August 7 a destructive hurricane swept the Island of Montserrat, West Indies. It appears to have originated on August 3, in latitude 11° 51′ N., and longitude 35° 42′ W., or farther east than any tropical storm hitherto recorded. During the week August 24-30, it remained almost stationary in mid-Atlantic, traversed the Azores on September 3, touched Brest on September 7, and Corsica on September 9. Its full period was thirty-six days. The outflow of lava from Vesuvius became on January 15 somewhat alarming, as it approached the lower station of the funicular railway, and passed along by the observatory. An earthquake occurred in Mexico on January 24. It lasted three minutes, and more than two hundred buildings were seriously damaged. On January 26 severe earthquakes were felt throughout Greece. Houses were destroyed at Philiatra and Kyparissia, and some damage was experienced at Corinth, Megara, Tripolitza, Sparta, Gythium, Patras and Pyrgos. Professor Milne's instruments, in the Isle of Wight, were shaken at 8h. 24m. 55s. on that morning. It has been pointed out that the greatest volcanic eruptions on Hawaii have occurred at times of minimum sunspots. It could not, then, have been unexpected that on July 4 the crater on the peak of Mauna Loa burst into violent action. On July 19 Etna suddenly threw to a height of three miles an enormous mass of vapour, lapilli, stones and scoriæ. On their descent, wooden flooring was burnt and straw set on fire, and holes a foot in diameter were made in the observatory roof. The eruption was accompanied by no perceptible movement of the earth, and at Catania, eighteen miles off, the seismograph was unaffected. On the same day (July 19) Rome was damaged by an earthquake. The shock, which lasted twelve seconds, was most felt at Frascati and Marino. Dr. Baratta attributes it to a seismic activity in the Alban Hills. On September 20 many lives were lost and much property destroyed by an earthquake in Asia Minor; and on the 27th severe shocks, even more calamitous, occurred at Darjeeling. On September 30 there was a destructive earthquake in the Moluccas; and on October 12 one of a violent character shook the Island of Ceram, in the Dutch East Indies, killed 4,000 persons, and utterly ruined the town of Amhei. Dr. Omori, Professor of Seismology at the Imperial University of Tokio, as a result of his observation of Japanese earthquakes, has pub lished some important conclusions. Generally speaking, the duration of an earthquake varies directly as the magnitude of the disturbed area, and inversely as the distance of the observing station from the place of origin. The average duration of the vertical component is about fourfifths that of the horizontal component. The period of the maximum movement, both horizontal and vertical, ranges between 0·53 and 17 seconds for slow undulations, and between 0·12 and 0·15 second for ripples. The range of the vertical motion is always less than that of the horizontal motion. Professor Milne remarks that the average velocity with which waves pass through the earth varies with the square root of the average depth of the path they follow. It appears that the elasticity which governs the transmission of the precursors of the real earthquake augments at the rate of about 1 per cent. for every mile of descent. Balloons have been used with increased success for exploring the atmosphere. The loftiest theoretical height which can be attained by such means is twelve miles, or with the aid of the sun's heat, fourteen miles. The greatest altitude actually reached is eleven miles by an unmanned balloon, and five miles and a half by an aeronaut. In the case of the descent of a balloon, it has been shown by Dr. Hergesell that the velocity of the fall is not accelerated, as is often stated, but, on the contrary, decreases in proportion to the greater height; so that the higher the point at which the descent begins, the less necessary it is to throw out ballast. Since April, 1898, more than a hundred unmanned balloons have been sent up from Trappes by M. de Bort. His most important observation is that the air is subject to an annual variation of temperature, even up to six and a half miles, the maximum being towards the end of summer, and the minimum towards the end of winter. Dr. Tuma has made several ascents for the purpose of investigating atmospheric electricity. He finds that the positive potential decreases with the greater height, so that positive charges must be accumulated in the lower regions of the air. But there is no evidence that the balloon was electrically charged, or that there was any danger of the ignition of hydrogen from such a cause. At the Blue Hill Observatory, Massachusetts, on February 21, an altitude of 12,440 feet was reached by a recording instrument attached to a string of tandem kites. The temperature was found to be 12° Fahr., whilst that at the surface was 40°. Mr. Pilcher, who had made great progress in the construction of an aerial machine which should soar as well as fly, attempted a flight on the last day of September. He had risen to a height of about sixty feet, when, a sharp gust of wind snapping the tail of his apparatus, he was precipitated to the earth and was mortally injured. In striking an average it is the custom, when the number of readings is small, to omit any single one that differs widely from the others. This is not fair, since if the reading is a high one a lower mean is obtained than if it had been less high. M. Vallier advances the correct method. With a limited number of readings that includes a widely divergent value for which there is no intrinsic improbability, take the arithmetical mean of all the values and add to it the quantity where S is the sum of the squares, and S, is the sum of the cubes of the differences from the arithmetical mean. - } S ASTRONOMY. The favourite theory of the sun's heat is based on the postulate that the solar mass is of homogeneous density. Dr. See contends that if a heterogeneous mass be assumed the duration that must be assigned to the sun's heating power is much greater than in the former case; and he has propounded the law that the absolute temperature of a nebula condensing under its own gravitation varies inversely as the radius of the contracting mass. As the greatest amount of heat is produced when the mass has reached its least dimensions and contraction is about to cease, it follows that the solar temperature is still rising. This he takes to be at the present moment 8,000° C., whilst the original temperature of the central nebula when the earth was thrown off was less than 40° C. The earth on ceasing to contract had risen to about 2,000° C., which is high enough to account for all known geological facts. In addition, Dr. See, claiming to have determined the potential of a heterogeneous sphere as caused by itself, finds that the energy developed by condensation is greater than in the case of a homogeneous sphere in the ratio of 176,868 to 100,000. As a result of M. Dunér's spectroscopic observations of the sun's rotation, it appears that a point on his equator moves with a uniform velocity of 2.054 kilometres a second round an axis, the inclination of which to the axis of the ecliptic is 18-12°, the longitude of the intersection of the sun's equator with the ecliptic being + 28-00°. It is the synodic velocity, however, that is thus determined. Messrs. Hartley and Ramage give spectroscopic reasons for believing that gallium is present in the sun. There is little doubt that the northern and southern hemispheres of the earth have not the same curvature, though the amount of difference has yet to be ascertained. It seems probable too that her shape is tetrahedral, the result of a contractional deformation; and Dr. Gregory has shown how geological facts uphold this theory. Further portions of the Photographic Atlas of the Moon have been published by the Paris Observatory. The authors, MM. Loewy and Puiseux, draw some interesting conclusions from the white patches and trails that they attribute to a scattering of volcanic dust. The fact that these trails cover all the inequalities of the surface on which they lie points to their recent origin; and their position can be explained only by the supposition that they were deposited under the influence of an atmosphere agitated by variable currents. Indeed the authors contend that there must have been, at one time, a much denser atmosphere than corresponds with its theoretical distribution between the earth and the moon, which would give the latter onlyth of the whole. They suppose that hydrogen was early lost, that other gases have been absorbed in chemical combination, and that water, unrepelled by lunar heat, has sunk into the interior. They believe that there now exists a residue of atmosphere which may yet be detected; that there is no surface liquid and no sign of erosion by water; and that there is no coating of ice in sight, not even at the poles, although some may exist in the circumpolar depressions. Messrs. Lowell and Drew confirm Schiaparelli's observation that Mercury rotates once during his revolution round the sun, and they record the appearance of lines and dark patches on the planet's disc. The yellowish colour of Venus they ascribe to an atmosphere, and they consider that she always presents to the sun the same aspect. Mars was found in possession of a number of new canals and lakes. The white South Polar cap was observed to diminish as the equinox approached. At the same time a dark line formed round it, and the grey tint of the south temperate zone assumed a distinct bluish green, suggestive of a growing vegetation. Later this colour changed through brown to a slowly brightening yellow. The projections often seen on the terminator of this planet are due, in Professor Pickering's opinion, to clouds in the Martian atmosphere. He had already suggested that the orb's mean temperature was high, and such a fact would help to explain the disappearance of cloud during the orb's day. The value of Mars' period of rotation is given by Professor Bakhuyzen as 24h. 37m. 22·66s. ± 0·0132s. Mr. Denning puts it at 24h. 37m. 22.70s. Vesta was found to have a polar compression of, the major diameter being almost in the direction of its orbit. Its rotation was completed in less than thirty hours. Herr Fauth has observed on several occasions a brilliant white spot, about 4" in diameter, on the north-eastern belt of Jupiter. The great red spot has become somewhat faint. Its motion, which had been accelerated, fell off to the extent of 1:48. ; but this change was irregular. Mr. Denning has recorded many markings moving at different rates. The quickest was a small dark spot in longitude 145°, which had a period about twenty-seven seconds less than that of the great red spot. The period of rotation of Satellite I. is 12h. 24m., and its orbital ellipticity is found to be greater than in 1892. Professor Barnard reports the periodic time of Satellite V. to be 11h. 57m. 22·647s. On March 18 Professor Pickering discovered by the photographic method that Saturn has a ninth satellite, which he has named Phoebe. Its period of revolution is about seventeen months, and so it must be the outermost of its companions. Its distance from Saturn may be about 7,500,000 miles, and its diameter may be between 100 and 200 miles. A spectroscopic examination of Saturn's rings has led Professor Hale to confirm the general opinion that they possess no atmosphere. Dr. Witt, exercising a discover's right, has named the new planet Eros, thus rejecting Professor Chandler's proposal to call it Pluto. An examination of photographs taken during 1893-6 shows that on a large proportion of the plates the planet had left traces. Its eccentricity is extreme. On approaching the sun it traverses in 322 days a distance of 61,000,000 miles, or 200,000 miles a day. The chief comets of the year were Brooks and Chase left over from 1898, a new one, discovered March 3 by Professor Swift, Tuttle in March, Tempel II. in May, Holmes and Tempel I. in June, and Giacobini, new, September 29. Meteoric showers have been feeble. A few Perseids fell on each night between August 9 and 13. The Leonids disappointed all hope except for those persons who, like Professor Pickering, expect the maximum year to be 1901-2. An excited anticipation enabled some observers on November 15 to see a multitude of "stars like silver balls shooting about everywhere." The sky was bright in one case and misty in another, and the time was between three and four o'clock in the afternoon, when Leo was below the horizon. Many new variables have been discovered, among which may be mentioned one in Andromeda, one in Vulpecula, and especially one of the Argol type, in Cygnus, with a period determined to be 4d. 13h. 45m. 2s. η The multiple stars, a Polaris and Pegasi, are shown to have variable velocities. Spectroscopic examination indicates a heterogeneous composition of the Orion nebula. CHEMISTRY. Professor Japp, in his address to the Chemical Section of the British Association in September, 1898, dealt largely with the subject of enantiomorphous bodies, and followed Pasteur in maintaining not only that optically active asymmetrical compounds are always the product of vital action, but that no selective agent that was not itself alive could separate the lævo-rotatory and dextro-rotatory elements of a racemic compound. Such a picking out could be effected by micro-organisms, and might be wrought by human intelligence, but it could never be accomplished by ordinary chemical or physical forces unaided by a living operator; and the chance synthesis of an optically active compound from inorganic materials was "absolutely inconceivable." Mr. Herbert Spencer and Professor Pearson challenged the reality of these comprehensive assertions; and further experiment and research were called for. Meanwhile the question has not been allowed to rest. Messrs. Kipping, Pope, Rich and Peachy have made careful investigations, of which some mention may be made. A mixture of 25 grams of sodium ammonium dextrotartrate with 5 grams of the corresponding lævotartrate in a 5 per cent. solution was found to have the specific rotation [a]D = + 15.60° instead of the calculated value [a]D + 15.76°. The separating crystals were removed at intervals of several days, with the following result: Total material = [a]D 30 g.+ 15.60° Sodium potassium dextrotartrate is isomorphous with the corresponding sodium ammonium lævotartrate, and forms a stable racemic compound with the isomeric lævotartrate at ordinary temperatures. |