5o8 



NATURE 



{_Sept. 29, 1 88 1 



probably ow ing to its relative weakness in comparison with the 

 red one, could not be observed. Green and blue lines of other 

 elements were also noticed, among which the most frequently 

 conspicuovis one, next to the yellow sodium-line, was, again, 

 the green line of magnesium. 



On Augu t 13, 1879, the nucleus of an emerald-green bohde, 

 as bright as Jupiter, pr" duced a splendid continuous spectrum 

 fi-om red to violet, exhibiting first a bright sodium-line, and im- 

 mediately af ter« ards the green magnesium-line also, and some 

 others, supposed to be those of copper, with two faint red lines. 

 A similar bolide on August 9, 1880, showed on the continuous 

 spectrum of its nucleus, besides the sodium-line very bright, 

 those of lithium distinctly, and many metallic lines in the green 

 and blue portions of the spectrum. 



This occurrence of carbon, magnesium, and other spectral 

 lines (possibly of iron) in the vapour-streaks of shooting-stars 

 and fireballs, establishes a more certain and unequivocal re- 

 semblance between their chemical compositions and those of 

 solid meteorites, than does the exhibition of the sodium-line, 

 which, as Herr von Konkoly observes, ir.ay possibly be due to 

 the original presence of saline particles in the air itself. But 

 its extreme brightness in some, and total absence in other 

 meteor-streaks, ;eems yet rather difficult to account for on that 

 supposition. On the other hand the detection of carbon, while 

 it agrees with the element's occurrence in siderites and carbon- 

 aceous aerolites, reminds us also of the abundant proofs which 

 Dr. Huggins and other spectroscopic observers have obtained 

 of the sime element's prevalence in comets. And indeed the 

 prolonged luminosity of meteor-streaks, with their complex 

 gaseous spectra proceeding for long courses of time from an 

 exceedingly attenuated atmosphere, is it-elf a physical riddle 

 whose explanation as a mere question of radiation can scarcely 

 be very different from what is demanded by the phenomenon 

 of self-luminosity in the known gaseous nebulEe and in the 

 envelopes of comets. 



Of Dr. Huggins' applications of sidereal spectroscopy to 

 neubulae and comets, it may be mentioned that the extremely 

 eventful discoveries are not individually named and noticed 

 among the many high encomiums rightly besto" ed upon that 

 refined use of the spectroscope, in the opening address. But 

 the results therefrom obtained were yet fully as revolutionising as 

 regards the prevailing theories of tho^e bodies, and of the general 

 plan of con-truction of the sidereal heavens, as some of the 

 spectroscopic discoveries described in the fifty-years' retro' pect 

 were (.ns is there lucidly related) thoroughly subversive of the 

 formerly existing views of the internal phyical condition of 

 the sun. 



If I have here ventured to disown, and to disclaim for myself 

 some of the major accomplishments of meteor-spectroscopy by 

 showing them to be the results of later, independent, and much 

 more perfect observations, it is because, in comparison with 

 the very significant amplification which those later observations 

 have effected in the subject, the ea^y recogniiion of the presence 

 of sodium in meteor-streaks can only claim to be regarded as a 

 slight and inconsiderable fir; t-adventure in a province of spec- 

 trum analysis, the additions and improvements subsequently 

 made in which have been attended with much more remarkable 

 success. 



In the wide and accurate survey of the admirable opening 

 discourse, which strays with truly lifelike fidelity over all the 

 broad domains, ihe well-won fields and gallantly-scaled citadels 

 of modern scientific knowledge, I shall, I trust, be pardoned 

 if, in a matter of very little estimation by itself, I thus attempt 

 to remove and ban'sh from the eulogies of the address a small 

 and unobtrusive and appiarently unconscious excrescence of the 

 otherwise harmless and innocent transgression, iitagnh compoture 

 ' pari'a. A. S. Herschel 



Collingwood, September 12 



Sun-Spots 

 Records concerning phenomena are considerably enhanced 

 in value if they include accurate determinations of the ft'w« of 

 occurrence. This appears specially applicable to solar pheno- 

 mena, and particularly to sun-spots, of which there must be 

 many thousands of exact delineations without precise record of 

 the times when the spots first appeared on the visible surface of 

 the sun. No doubt there are several reasons to account for this 

 unavoidable absence of valuable information ; amongst others 

 the intense brightness and heat of the sun make it an exceedingly 



disagreeable object for protracted telescopic inspection ; nor yet 

 are we in a position at present to photograph it continuously, so 

 that we are necessarily content to compare photographs taken at 

 intervals of perhaps many hours, and to assume, or at any rate 

 not to dispute, that events of great importance have not occurred 

 in the intervals. This is the more to be regretted because a 

 knowledge of solar events is comparatively of little importance 

 unless it helps us to ascertain what influence those events exercise 

 on the earth and its inhabitants; and it is obvious that in com- 

 paring solar and terrestrial phenomena the times of occurrences 

 are of essential importance, if only to avoid ascribing an undue 

 effect to a given cause. It thus follows ihat even an approximate 

 time of the appearance of sun-spots is not without v^ilue. On 

 these grounds, as well as on the score of magnitude, I communi- 

 cate the following particulars of a recent appearance, or outburst, 

 of sun-spots, which occurred within certain moderate limits of 

 time. I premise briefly that a photoheliograph is in daily use at 

 the Trigonometrical Survey Ofhce, Dehra Doon, India, of which 

 I have executive charge. At present the instrument yields but a 

 4-inch negative, w hich is merely a microscopic delineation of I J 

 million millions square miles of solar surface ; however, as surely 



tracing from sun negative taken at Dehra Observatory, Great Trigono- 

 metrical Survey of India. Latitude 30° 19' 29" N. ; Longitude 78° 5' 42" 

 E. Height above sea 2232 feet, on July 25, 1881, at 4.47 p m. local 

 apparent time. Spots visible in previous negative taken on the same 

 day at 3.58 p.m. are coloured black ; and the new spots which appeared 

 between 4 and 5 p.m. are surrounded by a dotted circle. 



as the sun shines, so surely are at least t"o negatives taken of it 

 daily. Interru) tions, even in a land of sunshine like this, 

 sometimes occur ; notably at the bursting of the monsoons, 

 which occurred here last month (July), when the photo- 

 grapher was compelled to take the sun whenever visible, 

 rather than not take him at all. Under this choice of alterna- 

 tions the first negative (or say Nj) on July 25, 1S81, was 

 taken at 3. 58 p.m. of local .apparent ume ; it exhibited several 

 sun-spots, as is now usual, and of which therefore little need 

 be said, since solar observers are well aware that the sun has for 

 some months past resumed a state of consideralile energy in 

 respect to developmeirt of features; the second negative, rr 

 N„, was taken at 4.47 p.m. On comparing N, and Nj it was 

 at'once seen that in the interval of 49m. a considerable group 

 of spots had appeared in the neighbourhood of the sun's centre. 

 It is exceedingly difficult to exhibit an exact delineation of spot^ 

 when the negative is on so minute a scale ; I however inclose a 

 sdver print, as well as a hand-tracing of N„, from which the poi 

 tion and magnitude of the group, i.e. the new group, mny be nearly 

 inferred. This new group consists of sixteen spots, of w hich no in- 

 dividual spot is notably large, but there is this peculiarity about 

 them all, that they exhibit hardly any penumbra, but consist almost 

 entirely of well-defined umbra ; what penumbra appears, is 



