Moulton, Forest Ray, 1872-1952 · New York, The Macmillan company · leaf 57
large arc O1O2 subtends anangle at Ci made by the respective perpendiculars to thesurface which exactly equals the angle at C3 subtended bythe smaller arc O3O4. Therefore in this case the change indirection of the plumb line is not proportional to the dis-tance traveled, for the same angular change… … CH. n, lO] THE EARTH 29 in case the earth were spherical, and only in case it werespherical, the next question is what the observations show.Except for irregularities of the surface, which are not underconsideration here, and the oblateness, which will be dis-cussed in Art. 12, the observations…
Astronomy
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