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
Iridium, osmium, platinum, ruthenium, tantalum, thorium, tungsten, uranium.
Not in Solar Spectrum.
Antimony, arsenic, bismuth, boron, nitrogen, caesium, 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.