C. S. Hastings—Spectra of the Limb and Center of the Sun. 871 
all the differences which I have invariably seen in repeated ex- 
aminations since the 17th of February. 
Others have, however, been suspected. Certain lines, which 
are strengthened in a region of spots like those above men- 
tioned, appear to be strengthened also near the edge, but do not 
undergo so marked a change. It is obvious that the differences 
should be most pronounced in the clearest sky, and such is the 
case. The closest examination has extended only from B to a 
short distance above F, as the plate glass of which the small 
prism is made has a decided yellow tint and absorbs the blue 
rays strongly. 
thin. The origin of the Fraunhofer lines, then, must be in the 
photosphere itself, which is in accordance with Lockyer’s 
views 
Any effects which the chromosphere might produce, we 
In the apparatus described, two similar re were also 
e 
= tae of 
two opposite edges of the sun were thus brought together, and 
e change in refrangibility due to the sun’s rotation was very 
hown. 
New Haven, April 3d, 1873. 
