FACTJL^E AND SUN-SPOTS. 643 



rapidly shattered in pieces. They appear generally in groups, though 

 single spots are seen at times. When a large one is divided into 

 parts, they seem to repel one another, and move away in various direc- 

 tions with great velocity ; it is not uncommon that this separation is 

 equal to one thousand miles in an hour. Respecting what is some- 

 times seen about or crossing spots, we call attention to the simultane- 

 ous observations of Mr. Carrington and Mr. Hodgson upon two lumi- 

 nous objects, resembling in shape two new moons, each 8,000 miles in 

 length and 2,000 miles wide : these, separated by at least 12,000 

 miles, came instantly into view at the edge of a large sun-spot, with a 

 brightness several times greater than the surrounding photosphere, 

 then passed eastward over the spot, and disappeared in about five min- 

 utes, having gone not less than 36,000 miles. In no way did the dis- 

 turbance apparently affect the shape of the spot (passing probably 

 above it). On the following evening a great magnetic storm and aurora 

 were decidedly manifest, and there can be little doubt that they were 

 connected with the event seen in the sun the day preceding. Like- 

 wise we know that a great solar storm is in progress when our north- 

 ern heavens are so beautifully illuminated with the northern light. 

 As to the formation of some spots they have been very slow, requiring 

 no small amount of time after the disappearance of the facular waves ; 

 again, as stated, some come and go in a few hours, and assume in some 

 cases huge dimensions as compared with any one thing on the earth. 

 A single spot has measured from 40,000 to 50,000 miles in diameter, 

 in which, as will be readily seen, we could put our earth for a standing 

 point of observation, and note how the vast facular waves roll and leap 

 about the edge of the spot, and also how the metallic rain is formed 

 from the warmer portions of the sun. In June, 1843, a solar spot 

 remained a week visible to the naked eye, having a diameter of about 

 77,000 miles ; and in 1837 a cluster of spots covered an area of nearly 

 4,000,000,000 square miles. When we call to mind that the small- 

 est spot which can be seen with the most powerful telescope must 

 have an area of about 50,000 miles, we can readily 6ee how large a 

 spot must be in order to be visible to the unaided eye. Pasteroff, 

 in 1828, measured a spot whose umbra had an extent four times greater 

 than the earth's surface. In August, 1858, a spot was measured by 

 Newall, and it had a diameter of 58,000 miles more, as you will see, 

 than seven times the diameter of the earth. The largest spot that has 

 ever been known to astronomy was no less in diameter than 153,500 

 miles, so that across this you could have placed side by side eighteen 

 globes as large as the earth ; and, when the depth of this cavity is 

 considered mathematically, the result shows that probably not less 

 than one hundred globes the size of our earth would have been requi- 

 site to bring it up to the photosphere of the sun. So numerous have 

 been the observations and measurements, that any attempt to present 

 them all would require many pages. 



