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Scientific Intelligence. 



published. 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 was 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, this is little evi- 

 dence of their absence from the sun itself ; were the whole earth 

 heated to the temperature of the sun, its spectrum would prob- 

 ably resemble that of the sun very closely. 



Elements in the Solar Spectrum. 



According to Intensity. 



According to Number. 



Iron (2000 + ) 

 Nickel. 

 Titanium. 

 Manganese. 

 Chromium. 

 Cobalt. 



Carbon (200+) 

 Vanadium. 

 Zirconium. 

 Cerium. 

 Calcium (75 + ) 

 Scandium. 

 Neodymium. 

 Lanthanum. 

 Yttrium. 

 Niobium. 

 Molybdenum. 

 Palladium/ 

 platinum, ruthenium, tantalum, thorium, 



Magnesium (20 + ) 



Sodium (11). 



Silicon. 



Strontium. 



Barium. 



Aluminium (4). 



Cadmium. 



Rhodium. 



Erbium. 



Zinc. 



Copper (2). 



Silver (2). 



G-lucinum (2). 



Germanium. 



Tin. 



Lead (1). 



Potassium (1). 



Calcium. Zirconium. 



Iron. Molybdenum. 



Hydrogen. Lanthanum. 



Sodium. Niobium. 



Nickel. Palladium. 



Mangnesium. Neodymium. 



Cobalt. Copper. 



Silicon. Zinc. 



Aluminium. Cadmium. 



Titanium. Cerium. 



Chromium. Glucinum. 



Manganese. Germanium. 



Strontium. Rhodium. 



Vanadium. Silver. 



Barium. Tin. 



Carbon. Lead. 



Scandium. Erbium. 



Yttrium. Potassium. 



Doubtful Elements. — Iridium, osmium, 

 tungsten, uranium. 



Not in Solar Spectrum. — Antimony, arsenic, bismuth, boron, nitrogen (vacuum 

 tube), caesium, gold, indium, mercury, phosphorus, rubidium, selenium, sulphur, 

 thallium, praeseodymium. 



Substances not yet tried. — Bromine, chlorine, iodine, fluorine, oxygen, tellurium, 

 gallium, holmium, thulium, terbium, etc. 



In conclusion, Prof. Rowland adds, "Even after comparing the 

 solar spectrum with all known elements, there are still many im- 

 portant lines not accounted for. Some of these I have accounted 

 for by silicon and there are probably many more. Of all known 

 substances this is the most difficult to bring out the lines in the 

 visible spectrum although it has a fine ultra-violet one. Possibly 

 iron may account for many more, and all the elements at a higher 

 temperature might develop more. Then, again, very rare ele 

 ments like scandium, vanadium, etc., when they have a strong 

 spectrum, may cause strong solar lines and thus we may look for 

 new and even rare elements to account for very many more. In- 

 deed, I find many lines accounted for by the rare elements in 

 gadolinite, samarskite and fergusonite other than yttrium, erbium, 

 scandium, praeseodymium, neodymium, lanthanum and cerium, 

 which I cannot identify yet and which may be without a name. 

 For this reason, and to discover rare elements, I intend finally to 



