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Article SOLAR SPOTS. ← Page 2 of 4 →
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Solar Spots.
above passage saw it , I certainly could not conceive it to be of the extreme exten the figures it . There was a great isolated spot preceding the group in question , at a considerable distance from il , which would seem as if belonging to it , when seen foreshortened , as the whole would be when first seen near the eastern verge ; and I am inclined to suspect that the writer must have included this also in his computation , separated though it really was by a considerable space . If otherwiseit must have been
, the longest upon record , to have measured nearly a sixth part of the solar diameter . Several extensive clusters of large spots were apparent on the sun ' s disc at the same time , but this group was the only one that I could detect without any magnifying aid , employing as usual a stained glass . The next which I have to notice , is the only single spot I have ever observed with the naked eye . All the others were compound , consisting of two or more , which seems in general the case . The large one recorded
by Sir W . Herschel in 1770 , as seen with the naked eye , was of the compound character . " By a view of it , " he says , " with a seven feet reflector , charged with a very high power , it appeared to he divided into parts . The largest of the two , on the 19 th of April , measured 1 ' 8 " 06 in diameter , which is equal iu length to more than 31 , 000 miles . Both together must have extended above 50 , 000 . " The single spot I allude toand which I noticed with the naked eyeon the 20 th of Julwas
, , y , probably about as big as this double one . It was then somewhat past the middle of its course , the state of the atmosphere preventing it from being seen sooner without magnifying aid . It presented the appearance of a black , triangular , or wedged shaped nucleus , ( lying nearly parallel with the sun ' s equator ) surrounded with a broad border or penumbra , of
an oblong form . A few minute spots appeared following in its vicinity , before it had far advanced , which vanished on its approach to the sun ' s centre . Vast and concentrated must have been the disturbing forces which revealed so large an undivided portion of the solar mass . Sir John Herschel ,- thus seeks to account for the causes of these mighty ami mysterious movements . Assuming the sun to have an immense atmosphere , of an oblately spheroidal form , the escape of heat must be greater from its polar than from its equatorial regionsbeing thicker at the latter
, ; hence circulatory movements would be generated to and from the sun ' s poles in the fluids covering its surface ; and these , modified by its rotation on its axis , may occasion the solar spots , which appear to be confined to two zones , about 35 degrees on each side of the equator . " The spots , " he says , in his late splendid work , " in this view of the subject , would come to be assimilated to those regions on the earth's surfacein which for the moment , hurricanes and tornadoes prevailthe
, , upper stratum being tempoj-alily carried downwards , displacing by its impetus the two strata of luminous matter beneath ; the upper , of course , to a greater extent than the lower : thus wholly or partially denuding the opaque surface of the sun below . Such processes cannot be unaccompanied with vorticose motions , which , left to themselves , die away by degrees and dissipate ; with this peculiarity , that their lower portions come to rest more speedilthan their breason of the greater
y upper , y resistance below , as well as remoteness from the point of action , which , lies in a higher region , so that their centre ( as seen in our waterspouts , which are nothing but small tornadoes ) appears to retreat upwards . Now , this agrees perfectly with what is observed during the obliteration of the solar spots , which appear as if filled in by the collapse of their sides , the penumbra closing in upon the spot , and disappearing after it . "
Note: This text has been automatically extracted via Optical Character Recognition (OCR) software.
Solar Spots.
above passage saw it , I certainly could not conceive it to be of the extreme exten the figures it . There was a great isolated spot preceding the group in question , at a considerable distance from il , which would seem as if belonging to it , when seen foreshortened , as the whole would be when first seen near the eastern verge ; and I am inclined to suspect that the writer must have included this also in his computation , separated though it really was by a considerable space . If otherwiseit must have been
, the longest upon record , to have measured nearly a sixth part of the solar diameter . Several extensive clusters of large spots were apparent on the sun ' s disc at the same time , but this group was the only one that I could detect without any magnifying aid , employing as usual a stained glass . The next which I have to notice , is the only single spot I have ever observed with the naked eye . All the others were compound , consisting of two or more , which seems in general the case . The large one recorded
by Sir W . Herschel in 1770 , as seen with the naked eye , was of the compound character . " By a view of it , " he says , " with a seven feet reflector , charged with a very high power , it appeared to he divided into parts . The largest of the two , on the 19 th of April , measured 1 ' 8 " 06 in diameter , which is equal iu length to more than 31 , 000 miles . Both together must have extended above 50 , 000 . " The single spot I allude toand which I noticed with the naked eyeon the 20 th of Julwas
, , y , probably about as big as this double one . It was then somewhat past the middle of its course , the state of the atmosphere preventing it from being seen sooner without magnifying aid . It presented the appearance of a black , triangular , or wedged shaped nucleus , ( lying nearly parallel with the sun ' s equator ) surrounded with a broad border or penumbra , of
an oblong form . A few minute spots appeared following in its vicinity , before it had far advanced , which vanished on its approach to the sun ' s centre . Vast and concentrated must have been the disturbing forces which revealed so large an undivided portion of the solar mass . Sir John Herschel ,- thus seeks to account for the causes of these mighty ami mysterious movements . Assuming the sun to have an immense atmosphere , of an oblately spheroidal form , the escape of heat must be greater from its polar than from its equatorial regionsbeing thicker at the latter
, ; hence circulatory movements would be generated to and from the sun ' s poles in the fluids covering its surface ; and these , modified by its rotation on its axis , may occasion the solar spots , which appear to be confined to two zones , about 35 degrees on each side of the equator . " The spots , " he says , in his late splendid work , " in this view of the subject , would come to be assimilated to those regions on the earth's surfacein which for the moment , hurricanes and tornadoes prevailthe
, , upper stratum being tempoj-alily carried downwards , displacing by its impetus the two strata of luminous matter beneath ; the upper , of course , to a greater extent than the lower : thus wholly or partially denuding the opaque surface of the sun below . Such processes cannot be unaccompanied with vorticose motions , which , left to themselves , die away by degrees and dissipate ; with this peculiarity , that their lower portions come to rest more speedilthan their breason of the greater
y upper , y resistance below , as well as remoteness from the point of action , which , lies in a higher region , so that their centre ( as seen in our waterspouts , which are nothing but small tornadoes ) appears to retreat upwards . Now , this agrees perfectly with what is observed during the obliteration of the solar spots , which appear as if filled in by the collapse of their sides , the penumbra closing in upon the spot , and disappearing after it . "