The _Johns Hopkins University Circular_, No. 85, issued in February,
contains Prof. Rowland's report of progress in spectrum work. The
spectra of all known elements, with the exception of a few gaseous ones,
or those too rare to be yet obtained, have been photographed in
connection with the solar spectrum, from the extreme ultra-violet down
to the D line, and eye observations have been made on many to the limit
of the solar spectrum. A table of standard wave lengths of the
impurities in the carbon poles extending to wave length 2,000 has been
constructed to measure wave lengths beyond the limits of the solar
spectrum. In addition to this, maps of the spectra of some of the
elements have been drawn up on a large scale, ready for publication, and
the greater part of the lines in the map of the solar spectrum have been
identified. The following rough table of the solar elements has been
constructed entirely according to Prof. Rowland's own observations,
although, of course, most of them have been given by others:
_Elements in the Sun, arranged according to Intensity and the Number of
Lines in the Solar Spectrum_.
According to intensity. According to number.
Calcium Zirconium Iron (2,000 or more) Magnesium (20 or more)
Iron Molybdenum Nickel Sodium (11)
Hydrogen Lanthanum Titanium Silicon
Sodium Niobium Manganese Strontium
Nickel Palladium Chromium Barium
Magnesium Neodymium Cobalt Aluminum (4)
Cobalt Copper Carbon (200 or more) Cadmium
Silicon Zinc Vanadium Rhodium
Aluminum Cadmium Zirconium Erbium
Titanium Cerium Cerium Zinc
Chromium Glucinum Calcium (75 or more) Copper (2)
Manganese Germanium Scandium Silver (2)
Strontium Rhodium Neodymium Glucinum (2)
Vanadium Silver Lanthanum Germanium
Barium Tin Yttrium Tin
Carbon Lead Niobium Lead (1)
Scandium Erbium Molybdenum Potassium (1)
Yttrium Potassium Palladium
_Doubtful Elements_.
Iridium, osmium, platinum, ruthenium, tantalum, thorium, tungsten,
uranium.
_Not in Solar Spectrum_.
Antimony, arsenic, bismuth, boron, nitrogen, cæsium, gold, indium,
mercury, phosphorus, rubidium, selenium, sulphur, thallium,
praseodymium.
With respect to these tables, Prof. Rowland adds: "The substances under
the head of 'Not in the Solar Spectrum' are often placed there because
the elements have few strong lines or none at all in the limit of the
solar spectrum when the arc spectrum, which I have used, is employed.
Thus, boron has only two strong lines at 2497. Again, the lines of
bismuth are all compound, and so too diffuse to appear in the solar
spectrum. Indeed, some good reason generally appears for their absence
from the solar spectrum. Of course, there is but little evidence of
their absence from the sun itself; were the whole earth heated to the
temperature of the sun, its spectrum would probably resemble that of the
sun very closely."
The powerful instrument used at Baltimore for photographing spectra, and
the measuring engine constructed to fit the photographs so that its
readings give the wave lengths of lines directly within 1/100 of a
division on Angström's scale, give the foregoing results a weight
superior to many others published.
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