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SCIENTIFIC SUMMARY. 
ASTRONOMY. 
The Surfs Photosphere . — The kind of solar observation set on foot by 
Schwabe and Carrington is now being employed in the most satisfactory 
manner by De La Rue, Stewart, and Loewig, and the first series — “ On the 
Nature of Sun-spots” — of their ‘‘Researches on Solar Physics,” published 
early in December — and, let us add, printed at the expense of Mr. De La Rue 
— is a most important contribution to an important subject. 
The authors have endeavoured to answer the following questions : — I. Is 
the umbra of a spot nearer the centre than its penumbra ? or, in other words* 
is it at a lower level ? II. Is the atmosphere of our luminary to be viewed as 
composed of heavy solid or heavy liquid matter, or is it rather of the nature 
of a cloud ? III. Is a spot, including both umbra and penumbra, a phenomenon 
which takes place beneath the level of the sun’s photosphere or above it ? 
Now with regard to I., we know that the sun has an atmosphere, and 
the effect of the refraction due to this atmosphere will be to lessen the ap- 
parent encroachment of the umbra upon that side of the penumbra lying 
nearest the centre of the disc, if we suppose the umbra to be the lowest. Still 
the encroachment will not be obliterated. 530 spots have been carefully 
examined from this point of view, and 456, or 86 per cent., are in favour of 
the assumption that the umbra is the lower stratum. With regard to II., 
it is held that faculse — and probably the whole photosphere — consist of 
solid or liquid bodies of a greater or less magnitude, either slowly sinking 
or suspended in equilibrio in a gaseous medium. A table is given, which 
indicates that an obvious explanation of a large per-centage of faculse being to- 
to the left of the spots, is that they have been uplifted from the area occupied 
by the spot, and have fallen to the left from being thrown into a region of 
greater velocity of rotation. It is difficult in the present state of our know- 
ledge, to grapple very successfully with III. ; but our authors are inclined to 
answer it in the affirmative. The concluding remarks of this memoir are 
of the utmost importance : — 
“ It would thus appear that the central part of a spot is nearer the sun’s 
centre than the penumbra, and that both the umbra and the penumbra are 
probably beneath the general level of the surrounding photosphere. Now 
the umbra or lowest part of a spot is much less luminous than the general 
photosphere. But what does this probably imply, according to the laws with 
which we are acquainted ? It implies that in a spot there is probably some 
matter of a lower temperature than the photosphere. For is it not now 
recognized as a law, that if a substance, or combination of substances, of 
indefinite thickness and surface of small reflecting power have all its par- 
