November 29, 1900] 



NATURE 



109 



Connection of the Spots with Prominences. 



In 1869, when a sun-spot maximum was approaching, 

 the prominences were classified by one of us into eruptive 

 and nebulous J the former showing many metallic lines, 

 the latter the hydrogen and helium lines chiefly. This 

 conclusion, which was published in 1870, was subsequently 

 confirmed and adopted by Secchi, Zollner, Sporer, Young 

 and Respighi. 



In the same year prominences on the sun's disc were 

 also observed by one of us by means of the C and F 

 lines.^ 



The eruptive prominences, unlike the nebulous ones, 

 were not observed in all heliographic latitudes ; but, 

 according to the extended observations of Tacchini and 

 Ricco, had their maxima in the same latitude as the spots. 

 This is especially well shown by the diagrams illustrating 

 the distribution of spots, faculfe, eruptions and pro- 

 tuberances which are given by Tacchini for 1 881-1887 in 

 the Metnoria delta Soc. degli Spettroscopisti Italiani, 

 1882-1888. These curves show in the most unmistak 

 able manner that the spots, faculaj and eruptive or 

 metallic prominences have their maximum frequency in 

 the same solar latitudes while the nebulous or quiet 

 prominences are more uniformly distributed, and even 

 have maxima in zones where spots are rarely observed. 

 This is corroborated by what Prof. Respighi many years 

 ago stated : 



" In correspondence with the maximum of spots, not 

 only does the number of the large protuberances 

 increase, but more than this — their distribution over the 

 solar surface is radically modified." 



In his observations. Prof. Young found that the H and 

 K lines of calcium were reversed in the chromosphere 

 as constantly as h or C, and the same lines " were also 

 found to be regularly reversed upon the body of the sun 

 itself, in the penumbra and immediate neighbourhood 

 of every important spot." - This result was confirmed 

 by the early ("1881) attempts of one of us to photograph 

 the spectra of the chromosphere and spots, and also by 

 eclipse photographs. In the photographic spectrum, the 

 H and K lines are by far the brightest of the chromo- 

 spheric lines, and this fact has been utilised by Hale 

 and Deslandres acting on a suggestion due to Janssen, 

 for the purpose of photographing at one exposure the 

 chromosphere and prominences, as well as the disc of 

 the sun itself, in the light of the K line. 



These photographs thus give us in K light the phe- 

 nomena which one of us first observed by the lines C 

 and F of hydrogen, and thereby present a record of the 

 prominences across the whole disc of the sun as well as 

 at the limb. 



In such photographs near sunspot maximum, the con- 

 centration of the prominences in zones parallel to the 

 equator is perfectly obvious at a glance. Eruptive or 

 metallic prominences dre thus seen to cover a much 

 larger area than the spots, so that we have the maximum 

 of solar activity indicated, not only by the increased 

 absorption phenomena indicated by the greater number 

 of the spots, but by the much greater radiation phe- 

 nomena of the metallic prominences ; and there seems 

 little doubt that in the future the measure of the change 

 in the amount of solar energy will be determined by the 

 amount and locus of the prominence area. 



Spots are, therefore, indications of excess of heat, 

 and not ,of its defect, as was suggested when the term 

 " screen ' was used for them. We know now that the 

 spots at maximum are really full of highly heated vapours 

 produced by the prominences, which are most numerous 

 when the solar atmosphere is most disturbed. 



The Indian meteorologists have abundantly proved 

 that' the increased radiation from the sun on the upper 

 1 /".^.i"., 17, p. 415- 



2 "Catalogue of Bright Lines in the Spectrum of the Chromosphere" 

 (1872). 



NO. 1622, VOL. 63] 



air currents at maximum is accompanied by a lower 

 temperature in the lower strata, and that with this dis- 

 turbance of the normal temperature we must expect pres- 

 sure changes. Chambers was the first to show that large 

 spotted area was accompanied by low pressures over the 

 land surface of India (" Abnormal Variations," p. r).. 



Passing, then, from the consideration of individual spots 

 to the zones of prominences, with which they are in all 

 probability associated, it is of the highest interest to note 

 the solar latitudes occupied when the crossings previously 

 referred to took place, as we then learn the belts of 

 prominences which are really effective in producing the 

 increased radiation. The area of these is much larger,, 

 and therefore a considerable difference of radiatioi> 

 must be expected. 



The greater disturbance of certain zones of solar lati- 

 tude seems to be more influential in causing the -I- pulse 

 than the amount of spotted area determined from spots 

 in various latitudes. 



It is all the more necessary to point this out because 

 the insignificance of the area occupied by the spots has 

 been used as an argument against any easily recognised, 

 connection between solar and terrestrial meteorological 

 changes.! 



Assuming two belts of prominences N. and S., lo"' 

 wide, with their centres over Lat. 16°, a sixth of the 

 sun's visible hemisphere would be in a state of dis- 

 turbance. 



{To be continued.) 



THE KITE WORK OF THE UN/ TED STATES 

 WEATHER BUREAU. 



"pARLY in the year 1898, the Congress of the United 

 -*-' States granted a sum of money, to be expended 

 under the direction of the Chief of the Weather Bureau, 

 for the establishment and maintenance of a series of 

 stations at which observations of the upper free air were 

 to be made by means of automatically recording 

 mechanisms attached to kites. This work was to be 

 undertaken primarily in the hope that daily simultaneous 



FiQ. I. — Kite with meteorograph in position. 



observations might be obtained at definite altitudes, thus 

 permitting the construction of daily synchronous charts 

 of pressure, temperature, and wind direction and velocity,, 

 which, when studied in connection with corresponding 

 surface charts, would admit of some advance being made 

 in the present system of weather forecasting, both iiv 

 accuracy and in the duration of the periods forecasted for. 

 Seventeen stations were established in the spring of 



1 " So far as (;an be judged from the magnitude of the sun-spots, the cyclical 

 variation of the magnitude of the sun's face free from spots is ver>' small 

 compared with the surface itself; and consequently, according to mathe- 

 matic principle, the effect on the elements of meteorological observation 

 for the whole earth ought also to be small " (Eliot, " Report on the Meteor- 

 ology of India in 1877," p. 2). 



