The Philosophical magazine; a journal of theoretical, experimental and applied physics . jawsof the slit wide apart they might escape notice.^^ With respectto the American eclipse. Professor Pickering, with an ordinarychemical spectroscope directed to the suns place during totality,saw a continuous spectrum with two or three brright lines, onenear E and a second near C Professor Young, while ex-amining a part of the prominence at +146°, saw C, near D, aline at 1250 + 20, and another at 1350 + 20, and the 1474 Kline very bright, but not equal to C and D3; but he observedthat the 1474 K line, un
The Philosophical magazine; a journal of theoretical, experimental and applied physics . jawsof the slit wide apart they might escape notice.^^ With respectto the American eclipse. Professor Pickering, with an ordinarychemical spectroscope directed to the suns place during totality,saw a continuous spectrum with two or three brright lines, onenear E and a second near C Professor Young, while ex-amining a part of the prominence at +146°, saw C, near D, aline at 1250 + 20, and another at 1350 + 20, and the 1474 Kline very bright, but not equal to C and D3; but he observedthat the 1474 K line, unlike C and Dg, extended across the spec-trum ; and on moving the slit away from the prominence it per-sisted, while Dg disappeared. He also believes that the twofaint lines between it and D3 behaved in like manner. On ex-amining a prominence on the other side of the sun, he observednine lines and a faint continuous spectrum without any traces ofdark lines in it. As to the second point, let us find what spectrum we oughtto obtain from a corona at a point on the earth where the limbs. of the sun and moon are in line,—that is, where the eclipse istotal exactly. the Corona is a Solar or Terrestrial Phenomenon. 119 Let A be a point on the earth where the sun is eclipsed;B C, limit of earth^s atmosphere;D, the moon;H E, photosphere of sun;E Y, the apparent if the corona be terrestrial, the light producing it mustbe reflected or separated from the atmosphere within the triangleABC. Join B D and produce to G. Then G is the most distant point from the limb on the sunsdisk from which light is reflected to A bj^ the atmosphere; andif the triangle E A F or angular extent of the corona from thesun is given, we can find Z E A G. The angles being small, . ^ . ^^ = ^v approximately. GE :CB:: ED: DC, therefore GE = CB^, . (1)and EF :CB::E A :CA, therefore Er = CB^; . (2) andED = EA—AD; and AD being small in proportion toE A, E D may without great error be taken as equal to E A.
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