ASTRONOMICAL PHENOMENA AND PROGRESS. 



Wine-years. 



Minimum 

 of Sun-spoU. 



1784,8 1784 



17HS.5 (?) 



1810.5 1811 



.. 1822 



Wine-years. 



Minimum 

 of Sun-spoU. 



1833.8 1834 



1841.0 1846 



1QXR 9 J 1857 



1856 ' 2 ^1858 



1867.2.. 1868 



Forms of Solar Protuberances. Prof. Tac- 

 cliini, of Palermo, observing solar protuber- 

 ances by the spectroscope, from March 1871, to 

 February, 1872, found that out of 2,903 pro- 

 tuberances only 234, or about eight per cent., 

 have the form of a tree or of a fan that is to say, 

 are narrow at the base, and spread out toward 

 the upper part, as if they were produced by vol- 

 canic eruptions, whereas, the remaining 92 per 

 cent, have a broad base, and taper upward 

 like a pyramid ; and seem, therefore, to be 

 due to a simple throwing up of the substances 

 of the chromosphere. He therefore regards 

 the general form of the protuberances to be in- 

 consistent with the existence of a solid crust on 

 the sun's surface. "When the chromosphere 

 is observed with large instruments and under 

 peculiarly favorable conditions it does not 

 present the appearance of a continuous level 

 stratum, as should be the case if it were solid, 

 pasty, or liquid, but often appears to be formed 

 of a continuous series of very distinct flames. 

 It looks, indeed, like a general conflagration, 

 more or less developed, which is incessantly 

 renewed with greater or less force, and with 

 especial violence in particular parts, where it 

 gives rise to the protuberances. In small in- 

 struments, on the contrary, the chromosphere 

 appears smooth, excepting certain parts where 

 the flames rise to an unusual height. In like 

 manner the details of the protuberances, and 

 especially their outlines, as observed with 

 small instruments, are not comparable with 

 those made with large telescopes, which must 

 necessarily afford a higher degree of definition. 



Tacchini next described certain observations 

 which tend to show that the so-called jets, 

 projected upward from the chromosphere, 

 have their counterpart in a descent of matter 

 from above, in a kind of solar rain, when a 

 mass or cloud of luminous hydrogen suspended 

 in the sun's atmosphere throws off filaments 

 on both sides, which gradually descend and 

 unite at the sun's edge, thereby forming a pro- 

 tu I Trance which exhibits the arborescent or 

 fan-like form usually attributed to an eruptive 

 jet. This is a new point of great interest. 



The theory which attributes the solar pro- 

 tuberances to violent eruptions, forcing their 

 way through a solid crust, or liquid of great 

 'ing power, may, Tacchini remarks, appear 

 to derive some support from the chemical 

 composition of the protuberances. If the 

 masses which project above the chromosphere 

 were found to contain many materials differ- 

 ent from those which compose the chromo- 

 sphere itself, there would be good reason for 

 regarding them as projected from the interior 

 of the sun. And, in fact, some of the pro- 

 tuberances have a somewhat complex chem- 



ical composition, the bright lines observed in 

 their spectra often corresponding to magne- 

 sium, iron, sodium, titanium, calcium, barium, 

 nickel, chromium, copper, together with eight 

 other lines which may belong to as many 

 different substances; in all, therefore, eigh- 

 teen elements, besides hydrogen and the ele- 

 ment provisionally named Helium which is 

 never absent, and represents the constant ma- 

 terial of the entire chromosphere. On August 

 27th last, in a single protuberance nine different 

 substances, represented by a brilliant spectrum 

 of twenty-four bright lines, nine of which be- 

 long to iron, were seen. 



Planetary Influence upon Solar Activity. 

 Those distinguished investigators of solar 

 phenomena, Messrs. Warren De La Rue, Bal- 

 four Stewart, and Benjamin Lowry, presented 

 to the Royal Society in March last the fruits 

 of their long and patient study of the teach- 

 ings of the sun-spot observations at Kew, 

 with relation to the influence exerted by the 

 planets Mercury, Venus, and Jupiter. The re- 

 port is as complete as could be made out of 

 the materials. With respect to the two plan- 

 ets nearest the sun, they say : " If we now ex- 

 amine the two tables for the planets Venus 

 and Mercury, we shall find in them indications 

 of a behavior of sun-spots appearing to have 

 reference to the positions of these planets, and 

 which seems to be of the. same nature for 

 both. This behavior may be characterized as 

 follows : the average size of a spot would ap- 

 pear to attain its maximum on that side of the 

 sun which is turned away from Venus or from 

 Mercury, and to have its minimum in the 

 neighborhood of Venus or of Mercury." And 

 their general conclusions are as follows: 



Wo leave it to others to remark upon the nature 

 and strength of the evidence now deduced as to a 

 connection of some sort between the behavior of 

 sun-spots and the positions of the planets Venus and 

 Mercury. We think, however, it must be allowed 

 that the investigation is one of interest and impor- 

 tance, and we trust that arrangements may be made 

 for the systematic continuance of solar observations 

 to such localities as will insure to us a daily picture 

 of the sun's disk. 



The influence of blank days in diminishing the 

 value of a series of sun-observations is very mani- 

 fest. We have been able to record the behavior 

 across the sun's disk of 421 groups of Carrington's 

 series for a total number of 885 groups, and we have 

 been able to record the same behavior for 873 out of 

 544 groups observed at Kew. Thus, out of a total 

 of 1,429 groups, \ve have only been able to record 

 the behavior or 794. Nor are the records which we 

 have obtained so perfect as we could wish, on ac- 

 count of blank days, which make interpolations 

 necessary. It is therefore of much importance for 

 the future of such researches as the present that 

 there should be several observing-stations so placed 

 that we may reckon on having at least a daily pict- 

 ure of the sun's disk. 



It will be easily seen that such observations are 

 very different from experiments which may be mul- 

 tiplied ad libitum ; for in this case Nature gives us 

 in a_year or in ten years a certain amount of infor- 

 mation, and no more ; while it depends upon our- 

 selves to make a good use of the information which 

 she affords. 



