lowing night it had apparently sunk from the 2d to the 3d magnitude. On the night of the 14th of May it was studied at the Cambridge Observatory, and was then reported to be of about the 3d magnitude. By the 19th its brilliancy had decreased by nearly two magnitudes, and it was then very near the limit of visibility to the naked eye. On the 20th it was no longer perceptible to the unaided vision, but could easily be seen through an opera-glass. The star had dwindled to the 9th magnitude by the 9th of June. The following was the table of magnitudes as estimated by Mr. B. A. Gould, of Cambridge (American Journal of Science, xlii., 124):

the gas consisted chiefly of hydrogen. Observations were also taken on several successive evenings, during which the continuous spectrum diminished in brightness more rapidly than the gaseous spectrum. Messrs. Huggins and Miller suggest, as their explanation of these brilliant phenomena, that, in consequence of some vast convulsion, larger quantities of gas were evolved from the star, that the hydrogen present was burning in combination with some other elements, and that the flaming gas had heated to vivid incandescence the solid matter of the photosphere. As the hydrogen was consumed, the phenomena would diminish in intensity and the star rapidly wane. The results of the observations of Messrs. Huggins and Miller were confirmed by those of Messrs. Stone and Carpenter, at the Royal Observatory, on the night of May 19th.

Humboldt, in his "Cosmos," gives the following list of temporary stars, which are recorded in history, with variable degrees of certainty as to items:

134 B. C., in Scorpio.

123 A. D., in Ophiuchus.

in Centauron.

June 9.

It was

One observer in Philadelphia says that he saw on the 23d of September, 1865, a brilliant star in Corona, not laid down in the maps. It was reported to have been seen in London, Canada West, about May 1st, when its brilliancy was about equal to that of & Coronæ, or between the 3d and 4th degrees of magnitude. seen in Ireland and England on the 12th of May, and in France on the 13th. The descriptions of the star given by all the foreign observers at that time agree with those of the various observers in this country. On the 16th of May it was observed and subjected to the spectrum analysis by William Huggins, F. R. S., and W. A. Miller, Prof. of Chemistry in King's College, London, whose applications of that new power to the solution of some astronomical problems have been among the most valuable scientific results of the year. At that time the magnitude of the new star was below the 3d. In the telescope it appeared to be enveloped in a faint nebulous haze, which extended to a considerable distance and faded away at the boundary. A comparative examination of neighboring stars showed that nebularity really existed about it. Its spectrum was unlike that of any other celestial body thus far examined. The light was compound, and had apparently emanated from two sources. The principal spectrum was analogous to that of the sun, evidently formed by the light of an incandescent solid or liquid photosphere, which has suffered absorption by vapors of an envelope cooler than itself. The second spectrum consisted of a few bright lines, indicating that the light by which it was formed was emitted by matter in the state of luminous gas. To the eye the star appeared nearly white; but as it flickered there was seen an occasional preponderance of yellow or blue. The lines of the second spectrum indicated that

173

The majority of these stars shone with great splendor when first seen. Only three of the known variable stars, according to Humboldt, have been less than the 1st magnitude at the height of their brilliancy. The star of 389 a. d. was for three weeks as bright as Venus, and then rapidly disappeared from view. That of 1572 was seen at mid-day on November 11th, and no longer visible in the following March. It was as bright as Sirius, and reached the lustre of Jupiter. The star of October, 1604, also exhibited great splendor. The stars of 393, 827, 1203, and 1609, are considered one and the same; and a reappearance is predicted in 2014-'5. The periods of visibility of these stars differ greatly. That of 389 was three weeks; of 827 four months; and of 1012 three months. Tycho Brahe's star in Cassiopeia (1572) shone for 17 months. Kepler's star in Cygnus was visible 21 years before it totally disappeared. It was seen again (as a star in the same position) in 1655, and was then of the 3d magnitude.

The star of 1866 appears to be identified with No. 2,765 of Argelander's zone + 26° marked

In a recent essay, M. Chacornan expresses the opinion that the sun is a liquid incandescent mass, surrounded by a dense and imperfectly transparent atmosphere. In this atmosphere the solar vapors, raised by evaporation from the liquid nucleus, ascend till acted upon by the cold of the celestial spaces, when they are converted into luminous crystals. He attributes the spots to the engulfment of vast areas of these photospheric crystals, which lose their brightness as they sink. Another observer speaks of "several roundish, isolated portions of luminous matters (having the appearance of icebergs floating in a black sea) in the centre of an umbra."

During the year ending August 1, 1866, 282 negatives of the sun were taken in 158 days by the heliograph at Kew. The areas of the spots and penumbra were accurately measured, and the heliometric latitude and longitude calculated.

Father Secchi has completed the reduction of magnetic observations made during the years 1859-65, and of sun-spots during the same period. The results show the reciprocal influence of periodic variations of spots and of amplitudes of the daily magnetic oscillations:

It will be observed that the minimum of spots corresponds to the minimum of magnetic variations.

Spectra of some of the Fixed Stars, the Moon, and Planets.-Messrs. Huggins and Miller have spent much time during the past two and a quarter years studying the spectra of the fixed stars. Very few nights were favorable for observations, owing to the ever-changing want of homogeneity in the earth's atmosphere. The light of bright stars is very feeble when subjected to the large dispersion necessary to give certainty and value to the comparison of the dark lines of stellar spectra with the bright lines of terrestrial matter. For the purpose of these examinations, Messrs. Huggins and Miller made great improvements in the apparatus employed, bringing it to a point of perfection hitherto unknown. About fifty stars were examined by them, but their principal efforts were concentrated upon three or four of the brightest, the spectra of which are as rich in lines as the sun. The few really fine nights which are available whilst a star is well situated for such observations in respect of altitude and

sun-setting, make the complete investigation of a star the work of some years.

Aldebaran (a Tauri)-a pale-red star-is strong in the orange, red, and green lines. Nine of its spectra are coincident with certain lines in the sun-spectrum, indicating the presence of sodium, magnesium, hydrogen, calcium, iron, bismuth, tellurium, antimony, mercury. No coincidence was observed with nitrogen, cobalt, tin, lead, cadmium, lithium, and barium.

a Orionis (Betelgeux)-an orange-tinted star-shows strong groups of lines, especially red, green, and blue. The lines are coincident with those of sodium, magnesium, calcium, iron, and bismuth.

ß Pegasi-of a fine yellow color-reveals the presence of sodium, magnesium, and perhaps barium. The absence of hydrogen lines in this star and also a Orionis, is an observation of considerable interest.

The spectrum of the brilliant white star Sirius is intense, but owing to its low altitude, the observation of the finer lines was rendered difficult by motions of the earth's atmosphere. Sodium, magnesium, hydrogen, and probably iron lines, were found. The hydrogen lines were strong. The white star, a Lyræ, strongly resembles Sirius through the spectroscope. The spectra of Capella, a white star, and Arcturus (red), are analogous to the sun. In the lastnamed star the sodium line was ascertained beyond a doubt. In Pollux, coincidences were remarked with the sodium, magnesium, and probably the iron lines. Sodium lines are discovered in a Cygni and Procyon.

In the moon, no other strong lines are visible than those of the solar spectrum, when the sun has a considerable altitude. The quantity of light from different parts of the moon is very different, but the lines of the spectrum are in every case the same. The result of these examinations is wholly negative as to the existence of any lunar atmosphere.

Lines of orange and red are discovered in the spectrum of Jupiter, which are attributed to the modification of solar light before reaching our atmosphere, and are therefore due probably to absorption by the atmosphere of Jupiter. On one night, the moon and Jupiter being near each other, the opportunity was seized to compare them directly with each other, and these lines were the only perceptible difference observed between the two bodies. Similar bands in the orange and red are seen in Saturn.

In Mars no lines were detected in the red, like those in Jupiter and Saturn, with the exception of two or three strong lines in the extreme red. The spectrum of Venus is of great beauty, corresponding with that of the sun.

Comets.-Comet 1, 1866, was an oval nebulous mass, surrounding a very minute and not very bright nucleus, which possessed no sensible magnitude in the telescope. The light of the coma was different from that of the minute nucleus. The latter was self-luminous,

and the matter of which it consisted was evidently in the state of ignited gas. The coma probably shone by reflected solar light-the spectrum of the light of the coma differing entirely from that characterizing the light emitted by the nucleus. The prism gives no information whether the matter forming the coma be solid, liquid, or gaseous, though terrestrial phenomena would suggest that the parts of a comet, which are bright by reflecting the sun's light, are probably in the condition of fog or cloud. The nitrogen line is the only one detected in the nucleus. We must wait for a comet of sufficient splendor to permit the satisfactory prismatic examination of its physical state during various changes of its perihelion passage.

Father Secchi, at Rome, in January, 1866, made a spectrum analysis of Tempel's comet, and found the light monochromatic (green), similar to that of the nebula in Orion. The monochromatic condition of the light he attributes to a molecular constitution different from that which forms the planets and stars. He infers that not all the light which comes from the comet is reflected from the sun, or, if it is so, that it suffers a singular sort of absorption. The spectrum of the comet exhibited three principal lines on a faintly-shaded ground. The latter is probably due to light reflected from the sun; the residue, the light of the comet itself.

Influence of the Tidal Wave on the Moon's Motion. Mr. Adams and M. Delaunay, have shown by their recent investigations that the change in the eccentricity of the earth's orbit accounts for only about one-half of the secular acceleration of the moon's motion, viz., about six seconds in a century. Prof. Harrison suggests that the other half might be accounted for simply by assuming that the length of the sidereal day has increased by merely .01197 of a second in the course of 2,000 years. M. Delaunay subsequently showed that the retarding effect of the tidal wave, originally pointed out by M. Mayer, twenty years ago, sufficed to account for the increase required in the length of the day. He concluded that the six seconds of acceleration resulting from the change of eccentricity in the earth's orbit are real, but that the other six seconds are only apparent. At a still later date M. Delaunay admitted that the tides produce a real acceleration of the moon's motion. In a paper, published in the "Philosophical Magazine August, by Mr. Croll (the second on that subject by the author), he offered the following considerations to show that the solar wave must diminish the earth's motion around the common centre of gravity of the earth and moon, and must therefore accelerate the angular motion of the moon. Suppose the rotation of the earth to be reduced to that of the moon, viz., once a month. In that case the earth would always present the same side to the The lunar wave would of course exist

moon.

"last

the same as at present, but would remain stationary on the earth's surface. The solar wave would also exist the same as it does now, but would move round the earth once a month, instead of once in twenty-four hours as at present. However slow the motion, a considerable amount of heat would be generated by friction, The source from which the energy lost in the form of heat would be derived, would evidently be the rotation of the earth round the common centre of gravity; for it is to this source that the motion of the water is due. Now the effects which would take place under these circumstances do actually take place under the present order of things. The two sets of effects caused by the lunar and the solar waves do not interfere with each other; consequently the solar wave must be slowly consuming the vis viva of the earth's rotation round the common centre of gravity. It is this vis viva which keeps the earth and moon separate from each other. As the vis viva is consumed, the two must approach each other, and thus the angular motion of the moon be accelerated. The solar wave does not consume the vis viva of the moon's motion around the common centre, but only that of the earth. Since the earth is gradually approaching nearer to the moon in consequence of the consumption of centrifugal force, which keeps it separate from that orb, the moon must therefore be moving with all its original vis viva in an orbit which is gradually becoming less and less, and the period of its revolution is consequently diminishing in length. According to M. Croll's calculation, it is therefore merely a question of time-though the possible date of the catastrophe is incalculably remote-when the earth and moon shall come together.

The Zodiacal Light.-M. Liandier, in the Comptes Rendus, says that he has watched the zodiacal light for several years, during the evenings of February and March. In 1866 he observed it from the 19th of January to the 5th of May. He reports that it has the shape of a perfect cone, varing in luminosity and color from a dull gray to a silver white, its changing aspect probably being caused by the condition of our atmosphere. In February the summit of the cone reached Pleiades, and the Twins in May. Between January and May he found it to follow the zodiacal movements of the sun. M. Liandier believes the luminous cone to be a fragment of an immense atmosphere, which envelops the sun on all sides. If so, he says it may be expected to exercise an enormous pressure on the sun, with a great development of heat, and, if local variations occur, may explain the phenomena of sun-spots, through the reduction of temperature that would follow its diminished pressure.

Nebula. About sixty nebulæ, examined by Mr. Huggins during the past year, reveal a spectrum of one, two, or three bright lines. Their elements cannot be determined, and the material of the nebula is supposed to be luminous

The nebula which have thus far been examined may be divided into two great groups; one giving bright lines with a faint spectrum background, the other giving apparently a continuous spectrum. The nebula in the swordhandle of Orion exhibits three bright lines; and in Lord Rosse's telescope reveals a large number of very minute red stars, which do not furnish a visible spectrum. The bluish-green matter of this nebula has not yet been resolved. The question arises: Are all the unresolved nebulæ gaseous, and those which give a continuous spectrum clusters of stars? Half of the nebula which give a continuous spectrum have been resolved, while of the gaseous nebula none have certainly been resolved.

The Force which prolongs the Heat and Light of the Sun and other Fixed Stars.-Prof. Ennis, in his interesting treatise on the "Origin of the Stars," propounds the following theory of the force which has given so prolonged a duration to the light and heat of the sun: That the chemical force now active in the sun is the conversion or conservation of the atomic force of repulsion which once held the solar system in a nebulous condition-that condition being one of inconceivable rarity. This atomic force must have been inconceivably great, and, being indestructible, must still exist. In fact, it is now, and has long been, passing off as light and heat through conversion into chemical forces. But why suppose that the original repulsive force is converted into light and heat through chemical agencies, rather than through electricity or some other means? The answer is because the present action in the sun, and in the fixed stars, and the former action in our earth, all strongly indicate chemical action. This force now operates in the sun and other fixed stars by three methods.

First. There are reasons to believe, from the nature of matter, that the materials in the sun may possibly give out more heat than those in our earth. On this planet one substance gives out more heat than another of equal weight; as, for instance, a pound of hydrogen produces more than four times the heat of a pound of carbon. Between other elements there are similar differences. Chemical diversities seem endless in number, and immeasurable in extent. Every star, so far as yet known, has a different set of fixed lines in the spectrum, although there are certain resemblances between them. It may, therefore, be concluded that each star has, in part at least, its peculiar modifications of matter called simple elements. The peculiar elements of the sun may differ from ours in heat-producing power as much as ours differ from one another in den

sity, and this is as 256,700 (hydrogen) to 1 (platinum). The assumption that the materials of the sun can give out no more heat, pound per pound, than the materials of the earth, is therefore unfounded.

Second. The conditions for producing heat in the vast laboratory of the sun, are different from those with which we are familiar on this earth. Combustion, with us, is always between a gaseous body and another which may be either gaseous, liquid, or solid; while in the sun the chief combustion takes place between liquid materials, for the liquid body of the sun is the hottest. Pressure exercises an important influence on combustion; and the pressure of the atmosphere of the sun must be inconceivably great considering the height of the atmosphere and the powerful attraction of the sun; but even that is as nothing compared with the pressure in the liquid body of the sun, many thousand miles down. The force of chemical attraction which impels atoms to unite in collision, thereby causing heat, may be in some way more powerful in the sun than on the earth. The ether or ethers around the sun may contribute to the production of heat.

Third. New combustibles may now be preparing in the sun from materials which have already been burned. According to the nebular theory, what we call the simple elements are mere modifications of one general fundamental matter. These modifications have arisen during the process of condensation, and must still be forming in the sun, because the sun is eight times less dense than is required by the law of density in the solar system, and will continue to form until its fires are burned out, and its due density is reached. Our "simple elements" may be not only compounds but double compounds, or compounds that are the result of hundreds or thousands of compoundings. In this way there must have been, at different periods, entirely different sets of elements in the sun. After one set had combined, producing light and heat by the combination, the resulting compound products may have again combined, with the same effect of light and heat, and so on in a continuous line of changes until the sun has attained its proper density, its fires are extinguished, and it becomes a "lost star," like the earth and the other members of the solar system.

With regard to the ultimate identity of suns, planets, and moons, Prof. Ennis says: "We are really treading on a fixed star. Here we have an opportunity of leisurely observing how a fixed star appears after its light has gone out. As in a forest we note the progress of the oak, from the acorn to the tall tree, some just rising from the ground, others vigorous in the sapling growth, and others whose trunks are populated with mosses and lichens, and whose branches are alive with birds, so we can see like stages of progress among the heavenly bodies, our earth included. Some are glowing with the fervor of most intense heat; others, like our