232 ANNUAL REPORT SMITHSONIAN INSTITDTION, 1955 



45 minutes. The first recorded observation of one of these flares was 

 made by Carrington in 1859 and was described by him as follows : 



While engaged in the forenoon of Thursday, September 1, 1859, in taking my 

 customary observation of the forms and positions of the solar spots, an appear- 

 ance was witnessed, which I believe to be exceedingly rare. The image of the 

 sun's disk was, as usual with me, projected on to a plate of glass ... I had se- 

 cured diagrams of all the groups and detached spots . . . when, within the area 

 of the great north group (the size of which had previously excited general re- 

 mark), two patches of intensely bright light broke out . . . My first impression 

 was that by some chance a ray of light bad penetrated a hole in the screen at- 

 tached to the object-glass . . . for the brilliancy was fully equal to that of direct 

 sunlight ; but ... by causing the image to move ... I saw I was an unprepared 

 witness of a very different affair. I thereupon noted down the time by the 

 chronometer, and seeing the outburst to be very rapidly on the increase, I hastily 

 ran to call someone to witness the exhibition with me, and on returning within 

 60 seconds, was mortified to find that it was already much changed and enfeebled. 

 Very shortly afterwards the last trace was gone, and although I maintained a 

 strict watch for nearly an hour, no recurrence took place. The instant of the 

 first outburst was not 15 seconds different from 11.18 G. M. T., and 11.23 was 

 taken for the time of disappearance. In the lapse of 5 minutes, the two patches 

 of light traversed a space of about 35,000 miles ... It was impossible, on first 

 witnessing an appearance so similar to a sudden conflagration, not to expect a 

 considerable result in the way of alteration of the details of the group in which 

 it occurred; and I was certainly surprised, on referring to the sketch which I 

 had carefully and satisfactorily (and I may add fortunately) finished before the 

 occurrence, at finding myself unable to recognize any change whatever as having 

 taken place. The impression left upon me is, that the phenomenon took place 

 at an elevation considerably above the general surface of the sun, and, accordingly, 

 altogether above and over the great group in which it was seen projected. 



Carrinj^on, at the meeting of the Royal Astronomical Society in 

 November 1859, pointed out that a moderate but very marked mag- 

 netic disturbance was shown on the Kew magnetograms at about 

 11 : 20, September 1, of short duration, and that toward four hours 

 after midnight there commenced a great magnetic storm. Wliile the 

 contemporary occurrence might deserve noting, he would not have it 

 supposed that he even leaned toward hastily connecting them. 



Carrington drew attention to two magnetic disturbances: the first 

 was of short duration and synchronized with the observation of the 

 outburst; the second followed some 17 hours later and was a great 

 magnetic storm. He evidently suspected that they were connected in 

 some way with the flare. This suspicion was no doubt suggested by 

 the fact that a few years earlier Sabine and Wolf liad independently 

 found that there were similarities between the periodic variations in 

 sunspot frequency and the range of diurnal variation in different 

 components of the earth's magnetic field, such as declination, hori- 

 zontal intensity, and dip. 



The lower curve in figure 1 shows the diurnal variation in declina- 

 tion as measured at Greenwich from 1874 to 1923 and since 1923 at 

 the Abinger Magnetic Observatory. The smoothed curve for the 



