76 
Langley, and was made at the Alleghany Observatory in 
1873. The appearance suggested to Mr. Langley was that 
of snow-flakes spread over grey cloth. In order to see this 
wonderful structural detail of the solar surface, it is not 
only necessary that the telescope must be a good one, but 
the atmospheric conditions must also be very good. Anyone 
who has studied the surface of the sun must have noticed 
that the moments are very rare when the definition may be 
said to be good; and it is only at such moments when the 
practised eye can detect the structure, such as those who 
have made the drawings referred to, show. A careful com- 
parison of the drawings and the descriptions appears to me 
to indicate that the various observers all mean the same 
thing ; but, as is well known, two draughtsmen seldom give 
the same representation of the same object, — not even of any 
portion of the moon’s surface, could two exactly similar 
drawings be made by different artists, so difficult is it for 
the hand to delineate what the eye can see, and in the case 
of the sun the intervals of good definition are so fleeting 
that the imagination must influence the hand of the artist. 
Now this is not the case when we employ photography to 
supply the place of the eye and hand. This has been done 
in a most successful manner by M. J anssen. The photo- 
graph of the entire surface of the sun which I show by 
means of the optical lantern is on a small scale, and there- 
fore gives very little detail, but we see in those taken on a 
larger scale that the structure becomes visible. It will be 
noticed that when compared with Dr. Huggins’ drawing 
there is a great similarity between the drawing and the 
photograph. The term “ nodule ” used by Hersch el appears 
to me to be better than any other, but it would be equally 
as good to say that the appearance is that of a “ mosaic ” 
pavement. But any term fails to describe the real 
appearance. 
It is difl&cult to find words to describe the extreme beauty 
of M. Janssen’s photographs. In the photograph before you, 
