542 BEPOET— 1881. 



exceedingly easy, but the conditions of amplification, illumination, and definition 

 of details were combined in about the best possible manner for the observer's 



Eurpose, which was to maintain an accurate record of the solar spots, and very 

 requently of the faculse also, on a large scale ; these have been collected into five 

 volumes, and presented to the Royal Astronomical Society. 



The comparisons commence with the very remarkable and cyclonic group of 

 August and September, 1859, which was uniquely distinguished (so far as observa- 

 tions have hitherto gone) by the remarkable outbiu'st of intense white light, far 

 brighter than the photosphere itself, which fortunately was witnessed on the fore- 

 noon of September 1, by the late Messrs. Carrington and Hodgson, but which ]\Ir. 

 Howlett missed seeing by only a few minutes, ha\dng completed his drawings, and 

 so left the telescope. 



Other striking and, if they may be so termed, crucial groups, were compared 

 with the magnetic records — very notably the great spot of October, 1865, en- 

 gi'avings of which may be found in the volume of the ' Proceedings of the Royal 

 Astronomical Society ' for the year last mentioned ; as also the prodigious groups of 

 February, 1870, which were observed and drawn on the occasion of their reappear- 

 ance, by revolution, in the three consecutive months of February, March, and April 

 of that year ; and on the last of which months the total displacement, at one and the 

 same time, of the solar photosphere — or, in other words, the total area occupied by 

 the sun-spots — was no less than 5,000,200,000,000 square mUes, or about twenty- 

 seven times that of the superficies of the earth ! 



So again, in August and September, 1870, immense groups, occupying from 

 4,000,000,000 to 5,000,000,000 square miles, were observed to make two consecutive 

 revolutions — [on the latter of which two occasions a beautifully enlarged photo- 

 graph of the sun, twenty-four inches in diameter, was made by Mr. Titterton, of Ely, 

 under the auspices of the late Canon Sehvyn, and was exhibited to Section A.] 

 On all these occasions great magnetic disturbances, amounting often to absolute 

 magnetic storms, were unequivocally manifested ; and, in fact, out of twenty-four 

 comparisons instituted, the following is the summary of results ; as showing the 

 coincidence of extensive solar activity and synchronous magnetic disturbance : — 



Intensely ...... 



Very decidedly ..... 



Decidedly 9 {.„-, m .- 



Moderately o ^21 aflJrmative 



Negatively, no spots, no storms during I 

 the year 1879 ( 



Questionable 1 I o 



Contradictory 2] ^ negative 



24 



Thus, then, from the data collected, it would certainly appear that, not only on 

 the occasion of large groups of spots occurring at the periods of maximum, but also 

 often on the occasion of any other marked outbursts of spots, there will generally 

 be found to be a corresponding amount of terrestrial magnetic distvu-bance. But 

 still, from an impartial and careful comparison of the data appealed to, it is clear that 

 the magnetic disturbances were manifested in a variety of ways, not only as regards 

 the extent — for instance, of the excursions of the needle, the rapidity of the oscilla- 

 tions, or the persistency of the more moderate disturbances, — but also the varying 

 intervals of time at which the disturbances take place, after the commencement of 

 the observed solar outbursts. 



With respect, lastly, to other reactionary influences, the Director of the Kew 

 Observatory states that, on the occasion of the perihelion passage of the Comet b,. 

 1881, on the 16th day of June last, the terrestrial magnetic curves were unusually 

 quiescent. 



9. On Magnetic Disturbances and Earth-currents. By Professor "W". 

 Geylls Adams, F.B.S.—See Reports, p. 463. 



