426 
ME. B. STEWAET ON THE OEEAT MAONETIC DISTTJEBANCE 
For the declination a departure of about . . . +2° 20' 
For the horizontal force — -04 of the whole. 
For the vertical force • • — ‘01 of the whole. 
The second great disturbance commenced very abruptly on September 2, at 5 a.m. In 
character it was similar to that of Amg-ust 28, its mean tendency being to increase the 
declination, and to diminish the horizontal and vertical components of the earth’s 
magnetic force. 
It is impossible to state the greatest departures from the mean caused by this distm’b- 
ance ; but in all probability they equalled or even exceeded those of the first. In 
appearance, also, the second disturbance was similar to the first, and it lost its excessive 
character for all the elements simultaneously about 3'’ 40'” p.m. of the 2nd of Sep- 
tember ; but, as has been already mentioned, and as may be seen from the lines of 
normals, it did not finally subside until September 7. 
After it had somewhat abated, its nature was exhibited by that peculiar serrated 
appearance of the curves which has already been alluded to, and which is very promi- 
nent in those of September 3rd and 4th. This appearance, however, had ceased some 
time before the elements finally resumed their normal values. 
Such is a brief and very imperfect description of the leading features of this great 
magnetic storm, which for excessive violence of character and length of duration, I have 
been assured by General Sabine, has never been surpassed by any similar phenomenon 
which has occurred in his long and varied experience. 
But, besides these two remarkable disturbances into which it divides itself, this great 
storm comprehends a minor disturbance, not approaching these two in extent, but yet 
possessing an interest peculiar to itself, which entitles it to be mentioned. 
On September 1, a little before noon, Mr. B. C. Cakkington happened to be observing, 
by means of a telescope, a large spot which might then be seen on the surface of our 
luminary, when a remarkable appearance presented itself, which he thus describes in a 
communication to the Royal Astronomical Society. 
“While engaged in the forenoon of Thursday, September 1, 1859, in taking my 
customaiy observation of the forms and positions of the solar spots, an appearance was 
witnessed which I believe to be exceedingly rare. The image of the sun’s disc was, as 
usual with me, projected on to a plate of glass coated with distemper of a pale straw 
colour, and at a distance and under a power which presented a picture of about 
11 inches diameter. I had secured diagrams of all the groups and detached spots, and 
was engaged at the time in counting from a chronometer and recording the contacts of the 
spots with the cross-wires used in the observation, when within the area of the great 
north group (the size of which had previously excited general remark), two patches of 
intensely bright and white light broke out, in the positions indicated in the appended 
diagram by the letters A and B, and of the forms of the spaces left white. My first 
impression was, that by some chance a lay of light had penetrated a hole in tlie screen 
