

xxvni.] RATE OF ASCENT. 417 



it is given to man to witness, and very impressive indeed are 

 the phenomena recorded. These metallic prominences are at 

 times observed shooting up almost instantaneously the exact 

 rate of motion I will state by and by to enormous heights ; 

 and not only are they seen to shoot up into the atmosphere with 

 very great velocity and with every indication of the most violent 

 disturbance, but their ascent is accompanied by most violent 

 lateral motions. We have means, both by actual observation in 

 the case of the up-rise of the prominences into the solar air and 

 in the change of the wave-lengths of the lines in the case of any 

 lateral motion, of determining how fast these violent prominences 

 rise and are driven by solar winds. 



Such prominences have been seen to mount upwards at the rate 

 of 250 miles a second, that is nearly 1,000,000 miles an hour ; 

 so that, if these gases continued their flight they would reach 

 the top of the solar atmosphere, if the solar atmosphere were 

 1,000,000 miles deep from the top down to the photosphere, in 

 about an hour's time. There are indications that these 

 prominences, instead of rising vertically, as we may imagine them 

 to do, are at times shot out sideways almost tangentially. In 

 that case, of course, the spectroscope enables us to determine the 

 velocity. 100 miles a second, either towards or from the eye, is 

 by no means an uncommon velocity, and there are also indi- 

 cations that, in the neighbourhood of the photosphere, where 

 these enormous prominences take their rise, vividly incandescent 

 hydrogen at a considerable pressure is present. 



The height of some of these prominences is very great. 

 Professor Young records one seen in 1878 as being nearly 

 400,000 miles high, that is 13 J minutes of arc, the solar radius 

 being 16 minutes. 



We have then, to sum up the effects of the ascents in the 

 order of intensity : 



1. Domes. 3. Quiet prominences. 



2. Metallic strata. 4. Metallic prominences. 



E E 



