70 Scientific Intelligence. 
4. On the distinction between spectral lines of Solar and Ter- 
restrial origin.—In a communication to the Physical Society, 
London, June 12, 1886, Professor M. A. Cornv calls attention to 
a method which allows one to distinguish instantly between solar 
lines and those due to the earth’s atmosphere in the solar spec- 
trum. This method is based upon a principle due to M. Fizeau, 
(Ann. de Chim. et de Phys., 4 série, t. xix, p. 211), that of the dis- 
placement of the spectral lines emitted by a source which is Jn 
absolute or relative motion. Professor Cornu shows that we shall 
have a variation of wave length equal to + » + or — ac- 
150°000 
cording as we take the same radiation at the eastern or western 
end of the solar equator, estimating the displacement in reference 
to the two D lines. It is found that the double displacement 
amounts to g$z of the distance between the two D lines. This 
displacement can be readily measured by the use of Thollon’s 
prisms or Rowland’s gratings. The experimental method con- 
sists in causing the image of the two extremities of the solar 
equator to fall alternately on the slit of the spectroscope. To 
effect this the beam of light passes through a condensing lens 
which produces in the plane of the slit a sharp image of the solar 
disk. A displacement of the lines of the spectrum due to the sun 
alone is produced by substituting one limb of the sun for the 
other, while the positions of the telluric lines are unaltered. Pro- 
fessor Cornu gives in detail the precautions which must be taken 
in the comparison. By causing the collecting lens to oscillate 
two or three times a second, the displacement becomes more evi- 
dent. The distinguishing of the lines is then easily accomplished. 
If the line remains immovable under this shaking process it is one 
belonging to the earth’s atmosphere, if it oscillates it is a solar 
line. Professor Cornu gives a map of Angstrém’s group. He 
indicates the telluric nature of a certain number of lines beyond 
the band 8, and shows that the line 1474 of Kirchhoff is a solar 
one. Since it oscillates we may conclude that the vapor which 
absorbs the radiations of which it takes the place is carried round 
by the rotation of the sun, and he shows that physicists and 
astronomers have now a method which will enable them to tell at 
a glance whether a spectral line belongs to the sun or the earth. 
— Phil. Mag., Nov. 1886, p. 458. To20s 
5. New form of Galvanometer.—In Wied. Ann., xxiii, p. 677, 
1884, Herr Rosenthal described a very sensitive galvanometer, 
in which the poles of the suspended magnet were brought very 
near the coils. Hr. J. Kollert has constructed a similar instru- 
ment which is more sensitive than that of Rosenthal. It consists 
of four coils whose axes all lie in the same horizontal plane; and 
the coils are placed radially in this plane. The magnets are 
made out of very thin watch spring in the form of ares of a cir- 
cle. Two such ares are placed at the extremity of a straight arm 
which is suspended horizontally from its middle point. The ends 
of the magnets can thus pass into the centers of the radial coils. — 
