There will be a total eclipse of the moon, visible at Greenwich, on July 12. The first contact with the penumbra will take place at 7h. 46m. P.M., first contact with the shadow at 8h. 45m. Totality will commence at 9h. 44m. and end at 11h. 24m. Last contact with the shadow will take place at 12h. 24m., last contact with the penumbra at 1h. 22m. on the morning of July 13. On July 27th there will be a partial eclipse of the sun invisible at Greenwich.

PROCEEDINGS OF THE ASTRONOMICAL SOCIETY.

Lieut. Herschel, in a paper on " Dark Objects crossing the Solar Disc," describes how he was for some time deceived into the belief that a flight of meteors was crossing the sun's face on October 17-18, 1869; but at length discovered that the objects he had been watching with so much attention were locusts.

Mr. Proctor contributes a paper "On the Solar Corona and the Zodiacal Light," with suggestions respecting observations to be made on the total solar eclipse of next December. He exhibits a series of arguments for rejecting the view put forward by Mr. Lockyer that the sun's corona is due simply to atmospheric glare, showing in particular that that portion of the sky on which the corona is projected during total eclipses corresponds to a portion of the atmosphere which is absolutely unilluminated by the sun. He gives reasons for believing the corona to be simply the condensed part of the zodiacal light. Remarking on Dr. Balfour Stewart's recent suggestion that the zodiacal light may be a terrestrial phenomenon, he points out that the trade-wind region (to the illumination of which by electric discharges Dr. Stewart ascribes the zodiacal light) occupies (above the horizon-plane of any station) a lamina shaped like a watch-glass, and the whole of this lamina (in other words, the whole sky) should be illuminated if the theory were correct. Were the zodiacal light caused in this way, a "tongueshaped slip" only of this lamina would be illuminated; and admitting this to be a possible arrangement at any time, we have yet no explanation of the fact that this slip always occupies a region near the ecliptic, or that it rises and sets with the stars. Among the suggestions put forward respecting modes of observing the eclipse, there is one which, remembering the very short duration of totality, seems to be worth consideration. When totality begins, the eye, accustomed to a brighter light, is unable to accommodate itself to the darkness of totality, nor does totality last long enough to admit of a change in this respect. If, however, the eye were kept in darkness before totality commenced, there seems little doubt that the observer would be able to employ much more effectually the two

minutes of total obscuration. This remark applies not only to general observation, but in an especial manner to those extremely delicate spectroscopic and polariscopic observations which are required in the present instance.

Captain Noble, observing Venus near her inferior conjunction, found the body of the planet projected very distinctly as a dark disc on a light background. "The difference of tint from that of the surrounding sky was evident," he says, "the instant Venus was regarded." This observation, though not new, deserves special attention just now that the nature of the solar corona is being so much inquired into. It shows beyond all possibility of question that there is some light which comes from regions beyond the planet; in other words, that there is just such illumination beyond Venus as we should expect to find if the corona is a solar appendage. It seems amazing that in the face of such evidence-with Venus actually projected as a dark disc on some illuminated region beyond her any astronomer should believe the light of the corona to come from the glare of our atmosphere some hundred miles or so, at farthest, from the earth.

Mr. Browning invites attention to farther changes in the form and colour of Jupiter's belt. The ochreish-yellow which had been so marked during the winter months of 1869 had, on January 31, become much fainter and of a duskier hue, being also confined to the northern part of the equatorial belt, instead of covering the whole of it as had before been the case. On March 10th, he found the tawny-yellow colour again extending over the whole of the equatorial belt, which had become broader than he had ever before seen it. This belt had a very dark band on the south, and a narrower dark band on the north; beyond each of these being a brilliant white belt. It will be interesting when the planet again returns to our skies (towards the end of the year) to observe whether the striking outbreak of colour has passed away or increased. The planet will not rise to a great height on the meridian, but the correcting eye-piece ingeniously contrived by Messrs. Airy and Simms will render observation at low elevations a very different matter from what it used to be.

At Mr. Hind's suggestion, Mr. Plummer, of Mr. Bishop's Observatory at Twickenham, has re-examined the orbit of the comet of 1683. He has been able to show that, instead of the ellipse calculated by Clausen, the orbit of the comet is probably parabolic or nearly so, so that there is very little probability that this famous comet will quickly return to the sun's neighbourhood.

Professor Wolf has continued his researches into the solar spotperiod. He finds that the observations made in the years 1864-69 supply clear evidence in favour of his theory that the spot-period is one of 11 years. But the most interesting part of his communi

cation is that which has reference to the relation between the variation of the magnetic declination and the frequency of solar spots. In 1859, Professor Wolf had proposed the following formula for this variation (v) at Christiania:

v = 0·0413 r + 4'·921,

where is the "relative number representing sun-spot frequency.' The following Table, in which v represents the calculated the observed variation, indicates what cannot but be regarded as a very satisfactory confirmation of this formula:

The observations of the magnetic variation were communicated to Professor Wolf by Messrs. Mohn and Fearnley. It will be seen at once that the minima of the two series closely accord. Doubtless, with the progress of observation, the empirical formula stated above will have to be slightly modified.

Mr. Birt supplies further notes on the visibility of the spots upon the floor of the lunar crater Plato. It seems too difficult to separate the different qualities of vision, the various conditions of the atmosphere, and still more the peculiarities of different telescopes, from the variations of visibility considered by Mr. Birt, to form any satisfactory conclusion on the subject.

Professor Cayley supplies two valuable papers on the geometrical theory of solar eclipses. The mode in which he treats the subject is too rigidly mathematical to admit of being presented in these pages. It may be remarked, however, that in his first paper he discusses, in a most lucid and interesting manner, the problem of determining the stereographic projection of the curve of two dimensions which is the intersection of a cone and a sphere, showing that this projection is a bicircular quartic.

4. BOTANY.

Cross-fertilization.-Dr. Ogle has continued his observations on the various contrivances in the structure of the flower to promote cross-fertilization. The purpose of the nectary is to attract insects; any noticeable irregularity of the corolla is also usually connected with the visits of insects, compelling them, when in search of the nectary, either to impinge on the anthers or on the stigma, and thus carry the pollen from one flower to another. Adrien de Jussieu had remarked the connection which exists between the presence of nec

taries and the irregularity of the flower, but had not discovered the reason of this connection. To speak of the tufts of hair-like papillæ which are often found on the pistil as collectors of pollen for the purpose of the self-fertilization of the flower, is clearly erroneous; their position shows that their use is the very opposite, serving to sweep the pollen out of the way in order to prevent it from reaching the stigma. Instead of poils collecteurs, by which term they are known in French manuals, poils expulseurs would be a better name for them. The heads of flowers of the order Compositæ usually begin to expand at the circumference, the expansion then extending to the centre. As a general rule the anthers are ripe before the stigmas (protandry of Hildebrand); the pollen, therefore, of the inner flowers fertilizes the pistil of the outer flowers; hence the outer flowers of the ray are generally destitute of stamens. Dr. Ogle finds that in Papilionacea cross-fertilization is the rule; and that the peculiar form of the stamens in Erica, Vaccinium, Arbutus, and other genera of the same order, contributes to this end.

Fertilization of Ferns.-Dr. E. Strasburger contributes a paper on this subject to Pringsheim's 'Jahrbuch für wissenschaftliche Botanik.' He commences the account of his experiments by tracing the development of the antheridia, or cells which produce the spermatozoids, from their earliest condition, and states that the growth of their lateral cells presents the first example in the vegetable kingdom of annular cell-formation by division. The new twin cells, a central cell and the annular lateral cells, are distinguished from ordinary cells by the differences of their contents, the inner one being stuffed with granular protoplasm, the outer ones containing at first an almost colourless sap, with a single scarcely discernible nucleus, and a few scattered grains of chlorophyll. After escaping from the antheridium, the spermatozoids, corresponding to the pollen of flowering plants, enter into the central cell of the archegonium, or female organ, by a peculiar twisting motion, and there meet with and fertilize the germ. A large number of the spermatozoids will enter a single cell, forming a kind of chain, but fertilization appears capable of being effected by one only.

Turning of Plants towards the Light.-M. Duchartre contributes to a recent number of the 'Comptes Rendus' an account of a remarkable growth of fungi in a garden at Meudon (Seine et Oise). They were found growing in a hollow place beneath a reservoir kept constantly full of water, in perfect darkness, but in a comparatively high temperature. At the end of September, on the lower surface of this reservoir were found more than 500 individuals of a small Agaric belonging to the genus Coprinus. They were all towards the southern part, springing from the roof of the cavity, with their head downwards. The stem of every individual had departed from the vertical by an angle of at least 30°, their

VOL. VII.

2 E

direction being towards the north. The circumstances seem to contradict the prevalent theory that the deflection of plants from the perpendicular is due either to the force of gravity, or to a desire to seek the light.

Sensitiveness of the Mimosa.-In the 'Mémoires de la Société des Sciences Naturelles de Strasbourg,' M. Millardet details some new and elaborate researches on the periodicity of the "tension" in plants, especially in the Mimosa pudica, or sensitive plant. The amount of "tension" is greater by night than by day, but undergoes various oscillations of two kinds, which he terms periodic and paratonic oscillations. The periodic oscillations are either long or short, the longer lasting for twenty-four hours, and attaining their maximum towards the end of the night, and their minimum towards the middle of the day; the shorter periodic oscillations lasting about an hour, and occurring both by day and night. The paratonic oscillations are due to differences in light, temperature, moisture, and other causes, and are more pronounced by day than by night; they are intermediate in duration between the longer and shorter periodic oscillations. All these movements occur in both stem and leaves. The motor organs of the leaves consist of tissues which are subject to variations of tension, and the movements are but an expression of these variations.

Variegation and Double-flowering.-It had long been laid down as a maxim by botanists that variegation of the leaves and doubling of the flowers (conversion of stamens into petals) never go together; and although recent writers had doubted the universality of the law, it was difficult to point to any authentic instances of the two phenomena occurring together. Professor E. Morren, of Liége, has, however, set the matter completely at rest by a description in the Belgique Horticole,' accompanied by a drawing, of a double wallflower with variegated leaves, which has been successfully grown for some years by M. Rodigas of St. Trond.

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Irritability of Stamens.-M. Jourdain has been trying experiments on the effects of chloroform on the stamens of Mahonia, which are excitable like those of the barberry, springing back against the pistil when irritated. When enclosed in a glass bell, in which was placed some cotton, on which a few drops of chloroform had been sprinkled, at the end of one minute the stamens were strongly thrown back as if in a tetanic state, and resisted all attempts at excitation. Exposed again to free air, after eight or ten minutes the irritability reappeared, at first feebly, and completely after the lapse of twenty-five or thirty minutes. If the action of the chloroform is continued for ten or twelve minutes the flower assumes an orange tint, and the stamens do not recover their sensibility on exposure to the air; the next day they become black.

'Comptes Rendus,' April, 25.