316 Royal Society : — 



given by various observers, have been collected together by Professor 

 Loomis, and published in a series of papers communicated by him to 

 the American Journal of Science and Arts. From all these accounts 

 there appears to have been two great displays, each commencing at 

 nearly the same absolute time throughout the globe ; the first on the 

 evening of the 28th of August, and the second on the early morning 

 of the 2nd of September, Greenwich time. 



Magnetic disturbances of unusual violence and very wide extent 

 were observed simultaneously with these displays. These were re- 

 corded more or less frequently at the different Observatories ; but at 

 Kew there is the advantage of a set of self-recording magnetographs, 

 which are in constant operation, and by means of which the state of the 

 elements of the earth's magnetic force may be known at any moment. 



The author then refers to curves, which accompany his paper, and 

 shows that the first disturbance commenced about 10^ on the 

 evening of August 28th, affecting all the elements simultaneously. 

 At about 7\ p.m., 29th August, the violence of this disturbance had 

 somewhat abated, and things remained nearly in this state until 

 September 2nd, 5 a.m., about which time another very abrupt 

 disturbance simultaneously affected all the elements, and continued 

 with great violence until about 4 p.m. of the same day, when it 

 somewhat abated. The elements, nevertheless, remained in a state 

 of considerable disturbance until September 5th, and only attained 

 their normal positions on September 7th. It thus appears that we 

 have two distinct well-marked disturbances, both commencing ab- 

 ruptly and ending gradually, the first of which began on the evening 

 of August 28, and the second on the early morning of September 2. 



These two great disturbances correspond, therefore, in point of 

 time, to the two great auroral displays already alluded to. 



The average effect of both of these disturbances was to increase 

 the declination, and to diminish the horizontal and vertical compo- 

 nents of the earth's magnetic force. 



The author then alludes to a disturbance which took place about 

 15 minutes past 11 o'clock on the forenoon of September 1st, simi- 

 lar in its mode of action to the two great disturbances already 

 mentioned, but not equalling them in extent or in duration. This 

 disturbance affected the magnetograph simultaneously with the 

 breaking out near a spot on the sun's disc, of a bright star, which 

 was fortunately observed both by Mr. Carrington and Mr. Hodgson, 

 independently 



The study of the curves furnished by the magnetograph during 

 this great storm, in the author's opinion, seems to throw light upon 

 the connexion which subsists between magnetic disturbances, earth- 

 currents, and auroral displays. These curves show that at the com- 

 mencement of the disturbance, the horizontal and vertical compo- 

 nents of the earth's force remained depressed below their normal 

 values for at least seven hours. The curves for this portion of time 

 have also a peculiar serrated appearance, as if on the great wave of 

 disturbance whose period was seven hours, there were superimposed 

 smaller waves whose period might be perhaps only a few minutes, or 

 even less. 



