186 Researches on Solar Physics. 
an example of this type, the air above it being composed chiefly 
of materials different from those of the ocean, but containing also 
aqueous vapor. On the other hand, we may imagine the sun’s 
photosphere to resemble a cloud, the characteristic of which is 
solid or liquid particles of a greater or less size existing ina 
gaseous atmosphere, composed to a greater or less extent of the 
lou 
materials of the ¢ hese points must be determined by 
through the refraction caused by a solar atmosphere, but we 
ilson observed, and which led him to the belief that the umbra 
was nearer the sun’s center than the penumbra. 
divided into six portions, comprising 30° each. 
[These sub-tables are omitted, the general results from them 
ries, } 
Result of Tare Il, Showing the effect of foreshortening in the direc- 
tion left and right of the central line. 
a, Giving the mean ratios between the two sides of the penumbra. 
Left of central line, 
Within 30° from left ween 30° and 60° from) Within 30° from central — 
limb. left limb. line. 
|The penumbra on the The penumbra on the The penumbra on th 
No. of | right side of & spot No. of right side of a » No. of right side of & pot 
pot a 
| being eq’ Y, | spots | bei. t i be ual to unity 
vobserved., that on the leftis | observed. ils oa the left in” Gaal that = the left is ; 
ieee | equal to equal to equal to 
130 | 18 119 14 a Be 12 
