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SCIENCE OF THE YEAR.

ASTRONOMY.

THE past year has been one of steady but slight sun-spot activity, with one considerable development in April. For future reference the two atlases of solar phenomena recently published will be of great value. That by M. Janssen shows the disc magnified to a diameter of four feet; the other gives its appearance in monochromatic light. The latter series has been taken by the spectro-heliograph at the Yerkes Observatory, the particular colour employed being that of the red calcium line. These photographs reveal flocculi exhibiting the distribution of calcium in the solar atmosphere, and promise results of the greatest importance.

Further evidence of the correlation between solar phenomena and magnetic storms has been furnished by Mr. E. W. Maunder, who finds that these disturbances are associated with the return of certain definite portions of the disc to the meridian, the conclusion being that the influence is not radiated equally in all directions, but proceeds in straight lines without spreading.

Recent observations by M. Charles Fabry indicate that the sun's luminosity is about 1,800 candle-power for each square millimetre of surface, whereas that of the positive pole of the electric arc does not exceed one-tenth of this amount on the average, though the figures are very variable.

No further evidence of the existence of an intra-Mercurial planet has been secured, but during the total eclipse of August 30, 1905, a special search will be made for any facts which will decide the question.

As regards Venus, Dr. Percival Lowell states that the marks on its surface are in no sense canaliform, being irregular in direction and width, and not in communication with one another. The planet makes one rotation in about 225 days, that is, in the period of a revolution.

Professor W. H. Pickering has recently announced some observations on the moon which recall those of Herschel recorded in the Philosophical Transactions for 1787. Changes have been seen on its surface which fall into three groups, explicable with ease as the result of hoar-frost, vegetation, and volcanic action, but difficult to account for on any other supposition. In reply to an obvious objection Professor Pickering urges that vast quantities of occluded water are given off from molten rocks during terrestrial volcanic eruptions, and that a much smaller exudation is all that need be postulated for his hypothesis.

A reduction of observations of the planet Eros gives 8.7966" 0·0047′′

as the value of the solar parallax, a value in close agreement with a recent determination by Sir David Gill.

Professor Lowell's observations on the Martian canals confirm the theory that they are due to vegetation, and, by inference, serve for artificial irrigation. Professor Denning finds that the rotation period of the canals is perfectly regular, and is complete in 24 h. 37 m. 22-7 s. In his opinion the supposed doubling of the canals is an optical illusion, but apparently he believes in the reality of the canals themselves. The inclination of the Martian equator to the Martian ecliptic is given as 22° 51'.

The great red spot on Jupiter continues under close observation, and minute variations of its period of rotation have been detected. The mean value is given as 9 h. 55 m. 39-5 s. in the first six months of 1904, as compared with 9 h. 55 m. 410 s. in 1903, and 9 h. 55 m. 39 s. in 1902. A variation of period of a similar kind has been noticed before, but the explanation has not yet been satisfactorily made out. The recent discovery of a sixth, and still more recently of a seventh, satellite to this planet is of great theoretical interest and importance.

The inclination of the orbit of Phoebe, Saturn's ninth satellite, is estimated at 6°, and its diameter at 200 miles. The apparent retrograde motion of this new member of Saturn's family is not yet firmly established. The satellites Titan and Japetus are said by M. Lucien Rudaux to have periods of rotation equal to their periods of revolution, like our moon, but a similar conclusion with regard to Rhea is regarded as pre

mature.

Dr. V. M. Slipher states in one of the Lowell Observatory Bulletins that free hydrogen is present in the atmosphere of Uranus, but is less abundant than in Neptune. Three bands situated at λ 510, λ 543 and A 577 point to the existence of gases in the latter planet analogous to hydrogen and helium, but not identical with either.

Among comets, the return of several of these wandering members of the universe, such as Encke's, and Temple's first and second, has been observed, and a few new ones of no great interest have made their appearance. The Perseid and Leonid meteoric showers have not presented any new features.

In the remoter regions of space the star Krueger 60, photographed by Mr. F. Schlesinger with the 40-inch Yerkes telescope, appears to have a parallax of 0.278 seconds, which would make it considerably nearer to the earth than a Centauri. The two components of the lastnamed are estimated to have a combined mass equal to 1.9 times that of the sun, and to have a mean distance from one another of 3:46 × 109 kilometres, or about 2,300,000,000 miles.

The repulsive force of radiation is believed to be sufficient to drive away cosmical particles, but to be inappreciable on masses of larger size. Professor Poynting, for example, estimates the total outward pressure of solar radiation on the earth as being equal to 70,000 tons, but this is far more than counterbalanced by the attractive force of gravitation, so that the effect of the sun's radiation on the earth will not produce a change of orbit of measurable magnitude for billions of years. On the other hand, a speck of dust, the hundred millionth of an inch in

diameter, would have its gravitational pull just balanced by the radiative outward push. If the particle were of less size it would be repelled like a comet's tail.

Professor Newcomb, in a first series of contributions to stellar statistics, discusses the position of the galactic and other planes to which the stars tend to crowd. The main stream of the galaxy is not along a great circle, as a determination of 42 points on this stream gives a latitude of 174°. This points to a small but well-marked displacement of our system towards Coma Berenicis, where the north galactic pole is situated. The same astronomer also shows that the star density increases considerably from the galactic poles towards the equator, even neglecting the condensation of the Milky Way. He concludes that the universe consists of two portions, one occupied by stars of a primary type, which occur in all regions, but especially in the Milky Way, and the other of the stars of secondary or tertiary types, uniformly distributed.

GEOLOGY.

From the report of the Coral Reef Committee of the Royal Society, we learn that the borings at Funafuti, one of the Ellice Islands, were finally carried to a depth of 1,114 feet, but it was only possible to secure 384 feet of core. In the first 150 feet, which gave 26 feet of core, the regular reef organisms were little changed; at greater depths the aragonite of the corals was gradually dissolved, the organisms of more resistive structure being left. At 400 feet the small amount of core procurable consisted of cavernous limestone, largely made up of foraminifera and casts of corals, the whole cemented by crystalline calcite. Foraminifera predominate still more between 637 and 748 feet, when the rock becomes soft and chalky-looking, crystalline dolomite replacing calcite as the cementing material. Hard dolomitic limestone follows, with frequent cavities, corals now being only represented by casts, with here and there a disposition to form alternate bands of corals and foraminifera with an excess of detritus.

Professor Judd and Dr. Hinde, who have compiled the report, have not definitely expressed their views on the formation of an atoll, but coral is shown not to grow below fifty fathoms, and characteristic sedimentary organisms are said to be absent from the core, hence it is almost certain that, as regards the upper 200 fathoms, Funafuti owes its formation to a change of level.

Professor A. Kamimura, in the Reports of the Physical and Mathematical Society of Tokyo, asserts that earthquakes are connected in some way with the phases of the moon, being most frequent at the times of conjunction, opposition, and quadrature. Various observations as to the velocity of earthquake waves are also due to him, and in fact the literature of this branch has received several important acquisitions during the year, for example, from R. Günther, who finds that the earth movements in the Bay of Naples are more extensive than was formerly supposed, and from Professor Láska, a member of the Austrian Earthquake Committee, who applies the effects of the Caraccas earthquake

to show that the shell of the earth is not more than 500 kilometres thick.

The gravitational anomalies under Etna, which are equivalent to the removal of a thickness of more than 1,000 metres of rock at the sea-level, from under the summit, are shown to be accompanied by magnetic irregularities. Probably the effect is due to a depressing of the root of the mountain into a denser magma, by the buoyancy of which the visible mass is supported.

Dr. Bijl, of the Royal Belgian Observatory at Uccle, finds from 685 determinations of the latitude of the station, taken between 1888-4 and 1899-5, that the range is about 0.7", with a maximum at 1898-6, a lower maximum at 1889-3 to 1889-4, and a minimum at 1889.0. This is equivalent to asserting that the north pole of the earth moves in like fashion, a phenomenon on which observations are much needed.

The recent important discovery that the seed-bearing habit existed among more than one group of palæozoic vegetation has attracted widespread notice. Professor Oliver and Dr. Scott, in the Philosophical Transactions, include them in a distinct class, to which they give the name Pteridospermia. The phylogeny of cycads, a race now only existing in diminishing numbers, is at last clear in its main outlines; they are sprung from this same pteridospermous stock, which in turn originated from a fern-like ancestor.

Messrs. Wright and Muff, in a memoir published by the Royal Dublin Society, conclude from British indications that a considerable proportion of the coast-line of South Britain is of Pre-glacial age, and that Ireland was isolated before the Glacial period. This conclusion increases the difficulty of assuming the extinction of the flora and fauna of Ireland during the maximum extension of the ice.

A serious bog slide took place on December 7 between Frenchpark and Castlerea, Co. Roscommon. A village was invaded, and a large area of agricultural land submerged. The movement continued for nearly three weeks, but the damage was principally done by the first onslaught.

The ancestry of the horse in Miocene and Oligocene times, instead of being traceable along a single line from the beginning, is stated by Professors Osborn, Ewart, and Ridgway to be referable to five sources, one leading to Neohipparion, the second an intermediate branch, leading through protohippus to equus, the third to the Upper Miocene Hypohippus, while the fourth and fifth did not survive the Miocene period.

A great number of bones of the dodo, the brevipennate parrot (Lopho-psittacus) and the Aphanapteryx, as also of land tortoises and other reptiles, have been discovered by M. Thirioux in a cave some 800 feet above sea-level not far from Port Louis (Mauritius).

The bold proposal of the Hon. C. A. Parsons at the British Association meeting to bore twelve miles into the earth in the interests of science deserves mention if only because the engineering difficulties are not deemed insurmountable by the author.

GEOGRAPHY.

The expeditions which have been exploring Antarctica are now yielding the fruit of their labours, and several interesting and valuable preliminary reports have been given. It will be remembered that the South Polar regions were attacked almost simultaneously by Captain Scott, the commander of the British expedition, from the New Zealand quarter; by Bruce, leading the Scottish expedition, from a diametrically opposite point; by Nordenskjöld, the Swedish explorer, from the South American quarter; and, lastly, by Dr. von Drygalski, directing the German expedition, from a point in the fourth quadrant, opposite to the Swedish expedition, having for his base Kerguelen Island. The geographical result of all these expeditions is to emphasize the probability that there is a vast irregularly shaped continent extending from Graham's Land, which is no doubt a subaqueous continuation of the South American continent, to Wilkes Land, a region stretching towards South Australia. The limits of this Antarctic continent are embraced by the Antarctic circle.

Bruce, by a series of soundings on a voyage of 5,000 miles in hitherto unexplored waters, confirms the conjecture of Captain Ross, that there is an extensive deep sea lying to the south of the Sandwich Islands, the average depth of the water being 2,500 fathoms.

Nordenskjöld has shown that there is an archipelago of islands bounding Graham's Land, but that Louis Philippe Land runs into King Oscar Land and forms with Graham's Land a continental region having high mountain peaks and extending inland into an ice-covered plateau. In the course of explorations scenery of the grandest description was met with, continental peaks on the one hand and bold rocky islands on the other presenting themselves to view, with a constant succession of glaciers and snow-capped promontories.

Dr. von Drygalski was only able to inspect land at the solitary peak of Gaussberg, but again, as far as could be seen, there was a vast tract of inland ice stretching towards the pole.

Although the record of new land discoveries may seem small, yet the expeditions have brought back a large number of exceedingly interesting observations on the climate, geology, and magnetic state of the South Polar regions. On all sides the weather appears to be most tempestuous, and it is one of the great hindrances to Antarctic discovery that the winds and storms are so violent. For a fortnight in May and June Nordenskjöld experienced winds blowing with an average velocity of forty-five miles per hour, accompanied with very low temperatures. In these latitudes the mean temperature of the year is only 10-2° F., and even the summer temperature is on the average only 28.2° F. Sometimes there are rapid and extensive fluctuations of temperature which are very trying, and Bruce records much fog and cloud. Zoologically there is great interest in the discovery of fossil bones of vertebrate animals, some of large size, and botanically of abundant remains of plants, so that here, as in the North Polar regions, a much milder climate must have prevailed at one time.

On September 10 the Discovery arrived at Portsmouth after a two

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