124. Sioux City Academy of Science and Letters. 



While the visible spectrum extends only about from 

 line A in the red to G or H in the violet, Professor Lang- 

 ley, of the Smithsonian Institution, by means of his mar- 

 velously delicate bolometer, has been able to detect dif- 

 ferences of heat radiations less than one-hundred mil- 

 lionth of a degree, Centigrade, and thus extend the 

 region of the infra red or heat spectrum, to a distance 

 of eight or ten times that of the portion visible to the 

 human eye; little, however, as to the constitution of the 

 sun has been learned from this source as yet. 



In the ultra violet direction the photographic plate 

 has extended our knowledge of this region to a distance 

 of about waA^e-length 2950, at which point the absorption 

 of the atmosphere puts a stop to further action on the 

 chemical plate. 



In 1889 Rowland published his great photographic 

 map of the solar spectrum, which was a monumental 

 document, and in the years 1895-1896 and 1897 published 

 his "Preliminary Tables of Solar Wave-Lengths" com- 

 prising over 20,000 lines, the accurate wave-length and 

 element to which each belonged being given. The fol- 

 lowing list of elements in the sun are taken from his 

 researches : 



Aluminum, Barium, Copper, Cobalt, Chromium, Car- 

 bon, Cerium, Calcium, Coronium, Cadmium, Erbium, Glu- 

 cinum, Galium, Germanium, Hydrogen, Helium, Iron, 

 Lead, Lanthanum, Magnesium, Manganese, Molybdenum, 

 Nickel, Niobium, Neodymium, Oxygen, Palladium, Potas- 

 sium, Rhodium, Sodium, Silicon, Scandium, Strontium, 

 Silver, Tin, Titanium, Vanadium, Yttrium, Zinc and Zir- 

 conium. Of the thirty-five or more remaining known 

 elements no trace could be found of sixteen of them, 

 eight were doubtful and the balance had not yet been 

 tried. It is possible though, as Rowland states, that all 

 the known elements may be present in the sun and that 

 if the whole earth were heated to the temperature of the 

 sun, its spectrum would probably resemble that of the 

 sun very closely.^^^ 



The solar spectrum differs from all other spectra in 

 the number and peculiarity of its dark lines, many thou- 

 sands of which have not yet been identified with known 

 terrestrial substances; but with the aid of the photo- 



