20 Turner, Total Solar Eclipses. 



instance, a particle would travel over a million miles — 

 more than a solar diameter ; and though a jet may retain 

 the same general appearance, though composed of entirely- 

 new matter, we might hope to detect differences of detail 

 in it. Good snapshots of Niagara, for instance, differ in 

 details, however quickly they may succeed each other. 

 Now pictures of the corona at an interval of one hour do 

 not differ in this way, and though we must not lay too 

 much stress on the evidence as yet, it affords a pre- 

 sumption in favour of lower velocities. Hence it is a 

 point gained that light-pressure enables us to look for 

 lower velocities of ejection. For instance, instead of the 

 382 miles per second necessary to eject a particle com- 

 pletely from the sun, one-tenth of this velocity only is- 

 required if the force be 100 times smaller, so that we may 

 now contemplate velocities of ten or twenty miles per 

 second, which would with such force raise a particle to a 

 height of several radii, as taking part in the phenomenon. 

 Now it is interesting to find that we have indications of 

 velocities of this size from a quite independent research, 

 namely, that on the Solar granules. The surface of the 

 sun in a telescope presents a mottled appearance. Forty 

 years ago, Mr. James Nasmyth, in a letter to a member 

 of this society — of which within a few months he became 

 a corresponding member — claimed that he had discovered 

 as an explanation of this mottled appearance, that there 

 were scattered over the sun's surface a number of objects 

 resembling " willow-leaves." Thereupon ensued a curious- 

 scientific controversy. Other observers saw the pheno- 

 menon indeed which Mr. Nasmyth intended to describe,, 

 but found fault with his description. Some preferred the 

 name "rice-grains" for the objects which they admitted 

 were there ; others spoke of bits of straw. Their various 

 ideas may be illustrated on the screen. Attention was 



