tentacles at their base, forms the so-called circular canal, while below it, and connecting with it, we have a large cavity forming the perivisceral cavity, a mode of development of the circular ring and of the perivisceral cavity totally unlike that observed in Ophiurans, Starfishes, Echini and Holothurians.

Metschnikoff compares the mode of development of the upper and lower cavity to analogous processes in the embryonic growth of Alcyonella and other Bryozoa; he traces a striking similarity in the structure and position of the digestive organs and tentacles with similar organs of Bryozoa. However that may be, he has shown conclusively that the larva of Comatula has apparently nothing in common with other Echinoderm larvæ; but we must wait for his figures on this intricate subject before we can decide if the position he assigns to Crinoids is true to nature. A. AG.

12. Chinese Botany.--We have received, through the kind attention of the author, a curious pamphlet, of 50 pages, On the Study and Value of Chinese Botanical Works, with Notes on the History of Plants and Geographical Botany from Chinese Sources; by Ě. BRETSCHNEIDER, M.D., Physician of the Russian Legation at Peking. Illustrated with 8 Chinese wood-cuts. Printed at Foo

chow. The preface bears the date of Dec. 17, 1870. In it the author declares that he is "neither a Sinologue nor a Botanist;" his "knowledge in Chinese as well as in botany being very limited." But his enquiries on the spot under advantageous conditions, and the use he has made of "the splendid library of the Russian Ecclesiastical Mission at Peking, where are to be found not only all Chinese works of importance, but also most European books relating to China," have not been fruitless. The pamphlet, not to speak of critical matters, is full of interesting information concerning esculent, medicinal, and other economical plants, natives of China or of early introduction, and the question of nativity or the source of introduction is treated of by the aid of Chinese documents, some of them of high antiquity. Cotton appears to have been of comparatively recent introduction, having reached China in the 9th or 10th century, from Central Asia and Cochin China. Contrary to some authorities, "it can be proved from Chinese sources that Maize and Tobacco are not indigenous in China." But the Batatas, or Sweet Potato, held to be of American origin, "was described in Chinese books a long time before the discovery of America, i. e., in the third or fourth century." Sugarcane did not pass from China to India, but the reverse, and as early as the second century B. C., although it was several centuries later that a native of India taught the Chinese to make crystallized "stone honey." sugar, or

A. G.

13. Plants killed by Frost: do they die in Freezing or in Thawing? That in certain cases plants die in freezing, is shown by Prof. Geppert, of Breslau, in a very satisfactory way, in an article in a recent number of Bot. Zeitung. The flowers of certain Orchids, notably the milk-white blossoms of Calanthe veratrifolia, produce indigo; but only upon a chemical reaction, which

takes effect upon the death of the parts. When crushed, or the cells in any way destroyed as to vitality, they turn blue immediately. Now, upon exposure to cold, the flowers turn blue at once upon freezing, showing that life then departed. Phaius grandiflores and other species of that genus are said to show the same thing.

III. ASTRONOMY.

A. G.

1. Scintillation of the Stars.-Prof. L. RESPIGHI has published an extended and very interesting paper upon this subject, it being an extract from the proceedings of the Accademia Pontificia de Nuovi Lincei, at the session held Febr. 14, 1869. It gives the results of a great number of observations made with the spectroscope upon stars of different magnitudes, and with every variety of circumstance as to elevation, azimuth, atmospheric conditions, and the like. The first portion of the paper is a resumé of an earlier one giving the results of a series of observations made previously to May 1868. The conclusions arrived at, although incomplete, were so important, that Prof. Respighi made a more extended series of over 700 observations, which were continued from October, 1868, to February, 1869. The instrument employed was an equatorial by Merz, with an aperture of 43 inches, and provided with a direct-vision prism by Hoffmann, with a cylindrical lens between the prism and the ocular.

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When the telescope was directed toward a star near the horizon, the spectrum of the star with its characteristic lines was seen, and in addition to these, broad bands, usually dark, very rarely ( bright, which slowly traversed the spectrum from one end to the other, passing from the violet to the red, when the star was in the east, and in the opposite direction when it was in the west. The characteristic phenomena, as summed up by Prof. Respighi, are as follows.

(1.) In normal atmospheric conditions, the motion of the bands is i from the red to the violet for stars in the west, and from the violet to the red for stars in the east.

(2.) Near the meridian, whether north or south, the motion generally oscillates from one color to the other, and sometimes the bands appear stationary, or traverse only a portion of the spectrum. (3.) The motion of the bands is more regular and less rapid near the horizon, while at greater altitudes it is less regular and more rapid.

(4.) When the instrument is so placed that the spectrum is vertical, the motion of the bands is the same as when it is horizontal, but the bands are less definite, and nearly transversal, up to an altitude of 30°; while for greater altitudes they become successively more indistinct, changing into longitudinal bands, and sometimes into mere moving masses either bright or obscure, and not rarely resulting in mere changes of brightness.

(5.) The bright bands are more rare and less regular than the dark ones, and occur only near the horizon.

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(6.) Not unfrequently, in the case of stars of low altitude, besides the bands which are regular, there occur other series of bands less regular and more inclined, and sometimes also longitudinal.

(7.) Under normal atmospheric conditions, neighboring stars all present the same phenomena.

(8.) Under abnormal conditions of the atmosphere, the bands are more feeble and more irregular in form and movement.

(9.) When high winds prevail, the bands are very faint and indistinct, and sometimes appear as mere changes of brightness in the spectrum, even when the stars are near the horizon, and very bright.

(10.) When the images of the stars are very diffuse, the bands are most feeble and indistinct.

(11.) When the bands are regular in form and movement, there is generally good weather; and it would appear in general that regularity in the phenomena of scintillation is a reliable basis for predicting the continuance of fair weather.

(12.) The phenomena of scintillation are most distinctly marked on evenings of greatest atmospheric humidity.

Prof. Respighi then discusses the cause of the scintillation as indicated by the phenomena observed. The regularity and constancy, both in direction and velocity, of the motion of the bands with respect to the meridian, namely, from red to violet for stars in the west, and from violet to red for those in the east, shows that it cannot be attributed to ascending or descending movements of the atmospheric masses, but must be due to some more general cause; and he concludes that this cause is the rotation of the earth, by which the luminous rays are carried through atmospheric strata of varying density.

For, in traversing the air, the path of the least refrangible rays would present the least deviation from a straight line, and that of the most refrangible the greatest. Of the rays which pass into the instrument or the eye therefore, the violet must enter the atmosphere at a more elevated point than the red rays. Hence the cone of rays if traced backward from the eye toward the star would be spread out into a vertical spectrum, with the most refrangible rays uppermost, and the others lying successively lower in their order. The curvature of the rays in passing through the air, as affecting the different rays in the same direction, may be neglected. Prof. Respighi finds by calculation, that for a star near the horizon, the breadth of this spectrum at a distance of 90 kilometers from the observer would be not less than 10 meters, and near the limits of the atmosphere it must be several times as great.

Now the rotation of the earth carries the luminous cone onward, causing the rays to traverse successively different portions of the atmosphere. If there are heterogeneous strata in the latter from condensation or rarefaction, these would act successively upon the different colors of the cone in their order. Toward the west, the motion of the air, relatively to the cone, is upward, and hence

the red rays of the latter are encountered by it first. In the east the phenomena occur in the reverse order, the violet rays being the first to be affected.

Now the dispersion of the rays, for a star near the horizon, corresponds to a very small angle at the eye of the observer, and a very slight increase or decrease in the density of a portion of the air may cause a considerable deflection of a ray from its normal path. If then the star observed is in the east, the mass of air will meet the violet end of the spectrum first, and as its refracting power is changed with its density, the violet rays will be deflected. They will thus be thrown out of the spectrum, causing a dark band, which will advance through the other colors, as the mass of air travels through the other portions of the cone of rays. If the star is toward the west, the mass of air will meet the red end of the spectrum first, and the dark band will pass from the red to the violet. At or near the north and south points, as the atmospheric motions would in general be transverse to the spectrum formed in the air, the bands, if formed at all would move in either direction indifferently, and present great irregularities.

As the elevation of the star increases, the length of the atmospheric spectrum becomes less and less, as the incidence of the rays becomes more nearly normal, and the bands traverse it with correspondingly greater velocity. Above 40° of altitude, Prof. Respighi has found that the cone of rays differs so little from a cylinder that the effects above described are scarcely perceptible.

Again, taking the divergence of the rays at the eye of the observer as about 11", which is probably near the truth, as the angle described by the earth in one second is 15", the time occupied by a dark band in passing the whole length of the spectrum would be somewhat less than one second, and in the observations the time was found to be not far from this.

Considering the complete agreement of these deductions with the phenomena observed, Prof. Respighi concludes that the cause of the scintillation is to be found in the actual subtraction of a portion of the rays by the unequal refraction of the masses of air through which they are caused to pass by the rotation of the earth, and he is thus led to reject both the explanation of Arago, according to which it is due to interference, and that of Montigny who ascribed it to the total reflection of a portion of the rays by strata of air unequally heated.

In the case of the planets, owing to the breadth of their disks, the spectra are superposed, and the phenomena are in general not distinctly seen, as they produce ordinarily simple changes of brightness, or mere irregular oscillatory movements of the images. In observations upon the brighter planets, however, especially Venus, when near the horizon, Prof. Respighi has occasionally, under favorable circumstances, recognized the same phenomena as are displayed by the fixed stars.

A. W. W.

2. On the recent Solar Eclipse; by J. NORMAN LOCKYER.Mr. Lockyer closes an interesting lecture on the Solar Eclipse, delivered before the Royal Institution, on March 17th, as follows:

I will proceed now, if you will allow me, to some of the general results obtained during the last eclipse.

I think that, although the work has been very unfortunately interrupted, still the result has been most satisfactory. By putting together observations here and observations there, I consider that our knowledge of the sun is enormously greater than it was a few months ago. For instance, we are enabled to understand the longneglected observation of Rayet, and the equally long-neglected observation of Pogson; and we know that outside the hydrogen there is, in all probability, a new element existing in a state of almost infinite tenuity. And we are sure of the existence of cool hydrogen above the hot hydrogen, a fact which seemed to be negatived by the eclipse of 1869.

I think, if we had merely determined that there was this cool hydrogen, all our labor would not have been in vain, as it shows the rapid reduction of temperature; but there is more behind. told you that M. Mädler, in summing up the observations made up to 1860, came to the conclusion that part of the corona was certainly solar, and that whether the outer portions were or were not solar, was a matter of doubt. I do not say that we have settled that absolutely, but we have firm evidence that some of the light of the corona is due to reflexion between the earth and the moon. The outer corona was observed to have a rosy tinge over the prominences, and the spectrum of the prominences was detected many minutes above them, as well as on the dark moon. It could not have got this color at the sun, for its intrinsic color is green, and the red light of the hydrogen supplied at the sun is abolished altogether, is absorbed, and can only reach the corona at the sun, so to speak, as dark light.

It is a great fact that we are sure, as far as observation can make us sure, that there is a glare around the hydrogen which gives us the spectrum of hot hydrogen on the corona, where we know that hot hydrogen does not exist. Assume the hot hydrogen which gives us the red light to be only two minutes high, the spectroscope has picked it up eight minutes from the sun! The region of cool hydrogen is exaggerated in the same way. We get it where there is no indication of the cool hydrogen existing. And then, with regard to the element which gives us the line of the green, we get that twenty minutes or twenty-five minutes away from the sun. Well, no man who knows anything about the matter will affirm

that it is certain that the element exists at that distance from the sun. Therefore I think we have absolutely established the fact that as the sun-the uneclipsed sun-gives us a glare around it, so each layer of the chromosphere gives us a glare around it. That is exactly what was to be expected, and that it is true is proved by the observation-a most important observation made in Spain