40 



ASTRONOMICAL PHENOMENA AND PROGRESS. 



nucleus, tlie chromosphere is generally very low and 

 sometimes totally wanting. 



At the nucleus, either there are no eruptions, or 

 they are confined to jets of great subtilty and little 

 duration. 



The nuclei of the spots are either totally obscure 

 or possess very feeble luminosity. 



Along the borders of the spotSj jets are thrown up 

 of extraordinary intensity and violence and of very 

 definite configuration. 



The jets adjoining the spots consist not solely of 

 hydrogen, but also of other substances, as is shown 

 by their respective bright lines in the spectrum. 



Among these bright lines which are commonly 

 found at the base or in the lower portions of the jets, 

 there are frequently seen those of sodium, magne- 

 sium, iron, etc., and constantly two lines in the red, 

 which do not correspond with those of any substance 

 yet known. 



Now and then, the eruptions in the vicinity of tho 

 spots assume gigantic proportions, and are probably 

 the cause of the rapid changes of form and position 

 which are observed in the spots themselves. 



There are often seen, in the neighborhood of the 

 spotsj jets curved backward upon the solar disk in 

 forms which are sensibly parabolic. 



The immense jets and erupted masses near the 

 spots expand and vanish away more rapidly than in 

 any other region. 



On the area of the spots, neither the photosphere 

 nor the edge of the sun's disk shows any perceptible 

 irregularity, that is, neither any perceptible promi- 

 nence nor depression. 



From all his spectroscopic observations the 

 author arrives at the following conclusions 

 among others : That the photosphere is the 

 surface of an incandescent liquid mass, or 

 stratum, by the weight of which various gases, 

 and especially hydrogen, are confined and 

 compressed in the interior of the sun at an 

 elevated temperature, under an enormous ten- 

 sion, and with a density differing but little 

 from that of the superincumbent liquid stratum. 

 That these gaseous masses in the interior, not 

 being in a condition of stable equilibrium, at 

 times burst forth with great force, developing 

 the jets which constitute the protuberances. 

 That the nuclei of the spots consist of portions 

 slightly projecting from the photosphere, of 

 solid masses or islands floating upon the liquid 

 stratum which envelops the body of the sun. 

 The immense chains of jets or protuberances, 

 which rise ordinarily in the region of the spots, 

 might be the cause of those great transforma- 

 tions which are observed in the latter, and 

 determine, by their resistance in the superficial 

 strata, currents in a direction opposite to that 

 of the solar rotation, from which would result 

 the proper motion of the spots themselves. 



Sun-Spots. Prof. Zollner addresses to the 

 Astronomuche Nackrichten, of March 2d, a 

 note on the periodicity and heliographic dis- 

 tribution of sun-spots. The following is its 

 substance : 



The sun-spots are wlaglike by the radiation of heat 

 on the glowing and liquid surface of the sun ; the 

 products of the cooling having again dissolved, in 

 consequence of the disturbanco of equilibrium pro- 

 duced by themselves in the atmosphere. When 

 these disturbances are not only local, but generally 

 distributed, the formation of new spots is but little 

 favored at the times of such general motion of the 

 atmosphere, because then the most essential condi- 



tions of the surface are wanting for a severe depres- 

 sion of temperature by radiation, namely : the rest 

 and clearness of the atmosphere. But, when the sur- 

 face has again gradually become quiet after the dis- 

 solution of the spots, the process again recommences, 

 and acquires in this manner a periodic character, in 

 consequence of the mean relationships of the surface 

 of the sun, which may be considered as attaining an 

 average in long periods. The distribution of the 

 spots in area must, according to this theory, be de- 

 termined by the zones of greatest atmospheric clear- 

 ness, which, as has been shown, generally coincide 

 with the zones of the greatest abundance of spots. 



A fine group of spots was observed to pass 

 the sun's centre in the Southern Hemisphere, 

 August 17th. The chief spot had an umbra 

 about 16,500 miles wide, and a penumbra 

 82,000 miles wide, and 46,000 miles long, vary- 

 ing in apparent size, however, from day to day, 

 and by the 25th of the month becoming quite 

 small. 



Mr. J. Birmingham, of Tuam, sent to Nature 

 the sketch of a remarkable sun-spot seen by 

 him May 6th and 7th. It was characterized 

 by a reddish-brown object like a cloud, which 

 seemed to hang over the nucleus of the umbra, 

 dividing it in two. The observer formed the 

 impression that it hung at a certain altitude 

 above the spot proper, and had no motion dis- 

 tinct from the latter. On the 8th of the month 

 this novel object had disappeared, and the 

 nucleus, formerly divided, was then in one. 



Mr. Stone, the newly-appointed Astronomer 

 Eoyal at the Cape of Good Hope, has com- 

 municated to the Koyal Society a paper com- 

 paring the curve representing the thermornet- 

 ric observations in that locality, taken there 

 since 1841, with a curve giving Wolf's obser- 

 vations of sun-spots. He says : 



The agreement between the curves appears to me 

 so close that I cannot but believe that the same cause 

 which leads to an excess of mean annual temperature 

 leads equally to a dissipation of solar spots. There 

 is on the whole a curious appearance of logging of the 

 inverse curve of solar spots over that of temperature. 

 At the maximum about 1856, this, however, does not 

 appear to be the case ; but, when the uncertainties of 

 the data, both of the solar spots near the minimum, 

 and of the mean temperature also, are taken into ac- 

 count, such discrepancies might perhaps fairly be ex- 

 pected, even if there be a physical connection between 

 the two phenomena as results of some common cause. 

 If there be a sensible inequality in the mean tempera- 

 ture with a period of about ten years, then the mean 

 temperature resulting from the observations in the 

 temporary observatory, which were made near a maxi- 

 mum, will be too high. The corresponding ordinatee. 

 therefore, will be depressed too much relatively to 

 those corresponding to observations made in the other 

 two observatories. I have imperfectly corrected the 

 mean of the results for the temporary observatory on 

 the supposition of such an inequality existing. The 

 only result of such a correction is to modify the curve 

 at the points _of junction of the observations made in 

 different positions. The general form is unaltered. 

 It should be mentioned that the point about which 

 the curves appear to differ most is near or at the 

 change of exposure from the original observatory to 

 the temporary shed about 1852. 



I may mention, that I had not the slightest expecta- 

 tion, on first laying down the curves, of any sensible 

 agreement resulting, but that I now consider the 

 agreement too close to be a matter of chance. I 

 should, however, rather lean to the opinion that the 



