6(24 PHILOSOPHICAL TRANSACTIONS. [anNO I7II, 



when longer on the sun. Again, May 5, 1/05, I could perceive two spurs or 

 branches, running from a spot, to change, and be sometimes darker, some- 

 times thinner. So March 30, 1706, I observed such another variation. This 

 day, or but little before, spots with faculae arose in the sun, which remained 

 not above three days. One of these spots I could manifestly perceive to be 

 sometimes quite extinct, and then again immediately to appear : and the faculae 

 also, in half an hour's time, had plainly altered their shapes. October 29 the 

 same year, I could plainly perceive the maculae and faculae both to change : and 

 while I was carefully viewing them, I saw a spot arise in one of the brightest 

 faculae, and again nearly disappear ; and then again appear strong and dark. 



Another thing I have observed, is, that the maculae do generally, if not 

 always, become nebulae or umbrae before they quite vanish ; and after that, 

 very frequently turn to faculae, or bright golden spots, more illustrious and 

 fulgent than the other parts of the sun. When the spots are of short duration, 

 faculae seldom ensue : or if they do, they are commonly the remains of some 

 spots that had before been seen on the sun, and vanished perhaps on the side 

 opposite to us. But spots that continue long, if they vanish before that part of 

 the sun revolves out of our sight, do very often become faculae. Of which the 

 table affords several instances, particularly July 3, 3 705. 



From these particulars, and their congruity to what we perceive in our own 

 globe, I gather, that the spots on the sun are caused by the eruption of some 

 new volcano therein ; which at first, pouring out a prodigious quantity of 

 smoke, and other opaque matter, causes the spots : and as that fuliginous mat- 

 ter decays and spends itself, and the volcano at last becomes more torrid and 

 flaming, so the spots decay and become umbrae, and at last faculae ; which 

 faculae I take to be no other than more flaming or brighter parts than any other 

 parts of the sun. These faculae I have observed never continue long on the 

 sun : and the reason I conceive is, because the volcano, after its smoke is over, 

 does not long emit its flames, because the fiery pabulum is then nearly spent, 

 when once it begins to flame : after which, the torrid volcano soon returns to 

 the natural temperature of the sun, so nearly at least as to escape our sight, at 

 so vast a distance from us. 



Another thing that may be accounted for, and which indeed in some measure 

 confirms what I have said, is the nuclei, or darker part of the spots generally 

 in most spots, and towards their middle. Now it is very usual in culinar)- fires 

 in this our globe, when they emit smoke, that the middle is the darkest part. 

 And so I take it to be in the eruptions of the sun ; that the nucleus is just over 

 the mouth of the ignivomous cavern, and that the misty parts of the spot are 

 the thinner parts of the smoke, swimming about in that fluid or atmosphere. 



