Cumming, Linnæus, b. 1843. [from old catalog] · New York, D. Van Nostrand · leaf 60
errestrial Magnetism. 4i spirit-level. The Ys are mounted on a framework D, D,having a circular limb which can be turned round in a hori-zontal plane, and is graduated within. A horizontal magnetneedle, F, is pivoted at the centre of the graduations. The zeroof these graduations should be in the… … Fig. 34. reading indicated by the end of the needle is the declination.The framework DD carries a vernier and clamp F, whichslides over a horizontal graduated circle forming part of thefixed base. This enables an observer with the telescope toset it in the astronomical meridian. The base is…
Electricity
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