744 Spectrum Analysis. [December, 
corroborated by the fadfs discovered by himself. By com- 
paring the dark lines of the solar spedtrum, of which he has 
formed a new and highly elaborate map, with the bright 
lines in the spedtra of metals volatilised by the eledtric 
spark, M. Kirchhoff has traced many other such coincidences 
as have been above referred to in the case of the sodium and 
potassium lines ; and he believes he can consequently assert 
with certainty the existence in the sun’s atmosphere of the 
elements iron, calcium, magnesium, sodium, chromium, 
nickel, cobalt, barium, copper, and zinc, whilst gold, silver, 
mercury, aluminium, cadmium, tin, lead, antimony, arsenic, 
strontium, lithium, and silicium appear to be wanting. 
According to his later investigations a considerable number 
of other elements, besides those above mentioned, are present 
in the solar atmosphere. The spedtrum of iron is remark- 
able for the great number of lines which it exhibits, and of 
these sixty were found to coincide with dark lines in the 
solar spearum. Allowing for a possible inaccuracy in his 
observations, M. Kirchhoff makes out the probability of his 
having confounded nearly coincident lines with one another 
in 60 concomitant cases to be equal to i divided by i, fol- 
lowed by 18 noughts— that is itself as good as nought. 
This, it is expedted, will bring home convidfion to the minds 
of the most doubting. Yet the inference from these coin- 
cidences to the necessary existence of iron in the solar 
atmosphere (or conversely) must remain inconclusive, if not 
inconsequential, as long as (besides the relation of the 
spedtra of compounds to those of their constituent elements) 
another question is not cleared up, of which M. Kirchhoff 
justly observes that it is one “ of great interest ’’—namely, 
whether the observed coincidences of lines belonging to two 
different substances, of which he has noticed some eleven, 
are real or apparent ones. 
Another important question, although without immediate 
bearing upon the point mooted, is whether a really element- 
ary body is capable of emitting several rays differing in 
quality, except such whose wave-lengths bear to each other 
the relation of harmonics, as indicated in the theory of 
Angstrom and Euler. An incidental result of the researches 
of M. Kirchhoff has been, or at least probably will be, the 
relinquishment of the somewhat fanciful notions conceining 
the internal structure of the sun hitherto current, and the 
re-adoption of the much more rational views of Newton and 
Galileo. Newton asked, “Are not the sun and the fixed 
stars great earths vehemently hot . . . whose parts are kept 
from fuming away, not only by their fixity, but also by the 
