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Cii. XXXIIL] 



AS SOUECES OF VOLCANIC HEAT. 



231 



SO that tliere are 9 of these cycles in a century. So late 

 as September 1, 1859, when the spots were very large, Hwo 

 observers, far apart and unknown to each other, were viewing 

 them with powerful telescopes, when suddenly, at the same 

 moment of time, both saw a strikingly brilliant luminous 

 appearance, like a cloud of light, far brighter than the general 

 surface of the sun, break out in the immediate neighbourhood 

 of one of the spots, and sweep across and beside it. It occu- 

 pied about five minutes in its passage, and in that time 

 travelled over a space on the sun's surface which could not 

 be estimated at less than 35,000 miles. A magnetic storm 

 was in progress at the time. Trom August 28 to September 4 

 many indications showed the earth to have been in a perfect 

 convulsion of electro-magnetism.' 



At Kew, Avhere there are self-registering magnetic instru- 



ments, by which the positions of three magnetic needles are 



recorded by photography, it was found that all three had 

 made a strongly marked jerk from their former positions at 

 the very moment when the bright light had been seen crossing 

 the solar spot. It would appear that the magnetic influence 

 had reached the earth at the same time with the lio-lit. 



' By degrees, accounts began to pour in of great Auroras 

 seen on the nights of those days, not only in these latitudes, 

 but at Eome, in the West Indies, on the tropics within 18° 

 of the equator (where they hardly ever appear), nay, what is 

 still more striking, in South America and in Australia, where, 

 at Melbourne, on the night of the 2nd of September, the 

 greatest Aurora ever seen there made its appearance. These 

 Auroras were accompanied with unusually great electro- 

 magnetic disturbances in every part of the world. In many 

 places the telegraphic wires struck work. At Washington 

 and Philadelphia, in America, the telegraph signal-men 

 received severe electric shocks. At a station in Norway the 

 telegraphic apparatus was set fire to; and at Boston, in 

 North America, a flame of fire followed the pen of Bain's 

 electric telegraph, which writes down the message upon 

 chemically prepared paper/ ^ 



^^ Herschel, Familiar Lectures on Sciontlfle Subjects, 1866, p. 80. 



M 



