. The Intellectual observer. or the admission of the light is marked d, and over one-half•of it is placed the right-angled prism e, to receive the lightfor the metallic spectra of comparison. The light of the is sent by the mirror f through a hole in the tube c tothe prism. The achromatic collimating lens is marked g, andthe two dispersing prisms of very dense glass h. The spectrumis viewed through a small achromatic telescope marked I,having a positive eye-piece magnifying nearly six: times. Thistelescope is carried by a micrometer screw q, capable ofdividing the space from A
. The Intellectual observer. or the admission of the light is marked d, and over one-half•of it is placed the right-angled prism e, to receive the lightfor the metallic spectra of comparison. The light of the is sent by the mirror f through a hole in the tube c tothe prism. The achromatic collimating lens is marked g, andthe two dispersing prisms of very dense glass h. The spectrumis viewed through a small achromatic telescope marked I,having a positive eye-piece magnifying nearly six: times. Thistelescope is carried by a micrometer screw q, capable ofdividing the space from A to H in the solar spectrum into 1800parts, and the telescope being furnished with a cross of wires,it is obvious the distances of the lines can be measured withextreme accuracy. The arm r carries the wires and forcepsconnected with the induction coil for deflagrating the metalswhose bright lines are examined for coincidence with the darkones of the stellar spectra. The prisms of this apparatus wore Celestial Chemistry. 391. 392 Celestial Chemistry. made by Mr. Ross, the cylindrical lens, and some other parts,by Mr. Browning, and the micrometer by Cooke and Sons. Inlater observations, two other prisms and another small teles-cope, made by Mr. Browning, were nsed, which, with lessdispersive power, afforded increased brilliancy, and were occa-sionally very useful. The excellence of the arrangement wasshewn by the sharp definition of the lines in the solar andmetallic spectra, and by its permitting a line between thedouble D of the solar spectrum, attributed by Kirchhoff tonickel, to be seen. THE MOON AND PLANETS. One of the first questions which presented itself to the mindsof the observers, was to test the existence or not of an atmos-phere to our satellite, the moon. On all astronomicalgrounds, the evidence of no appreciable atmosphere is verystrong; but there are other points connected with the subjectwhich have a little contrary tendency. It is clear that thesuns light, refl
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