Extracted text
Editorial transcription, lightly normalized from the scan. Line-break hyphenation, spacing, capitalization, and unmistakable OCR errors have been repaired; the claims remain those of The Flaming Sword.
EDITOR FLAMING SWORD:—A very prominent lawyer at Little Falls, N. Y., has asked me how I would account for the 8-inches-to-the-mile allowance for the earth's curvature, which the engineers who have surveyed for the Erie canal, made—8 inches to the mile for the entire length of the canal. "What became of this allowance? Does not the allowance prove that the earth is convex?" are the questions roughly stated. How would you answer?—Rev. U. G. Mitchell, Koreshan Missionary.
The engineers and surveyors make allowance for curvature in all their work where extended levels are desired, such as in the construction of canals. The fact that they are compelled to make this allowance is proof that a curvature exists, and must be considered in all such work; experience has taught them this. But we deny that the curvature for which allowance is made, is the curvature of the earth.
The surveyors and engineers employ optical instruments in laying out extended levels. The engineer levels his instrument, and reads a point in the signal staff placed at a given distance from the instrument; this point has an altitude in excess of the altitude of the cross hair. Assuming that the line of vision is straight (or nearly so), he concludes that the earth curves downward from the visual line. Of course, if it were known absolutely that the visual line is straight, a rectilinear extension of the optical axis of the instrument, the only conclusion possible would be that the earth curves away from the visual line at a specific ratio, and would therefore be convex.
A critical analysis of the facts with which the engineer has to deal, only proves that there is a divergence between the visual line and the earth; but the facts thus far do not prove the direction of the earth's curvature. The engineer does not make allowance for the full 8 inches to the mile; he has before him tables of "refraction," deduced from actual experience in surveying. The figures in the tables show the average ratio of divergence existing between the visual line and the earth, which is between 5 and 6 inches to the mile. The allowance is made for the curvature of vision from the earth's concave surface.
If one will turn to pages 50 to 57, of the CELLULAR COSMOGONY, and study the matter under the heads of "Horizontal Tangents from the Standpoint of the Surveyor;" "Horizontal Tangents in the Concave Earth," and "Appearances the Basis of Usual Geodetic Calculations," the subject will become clear to the mind. The diagrams on pages 51 and 52 represent the relation existing between the visual line and the earth on the basis of assumed convexity, and the actual relation as it obtains in surveying over the concave arc. The target P, on signal staff A, in diagram on page 52, at a distance of one mile from point of observation, exceeds, by 6 inches, the altitude of the leveled instrument at T; and all that is necessary to find the same altitude as the instrument at T, is to measure down the staff 6 inches, and thus make allowance for the upward curvature of the visual line from T to the target on staff A.
The source scans remain the record. This page preserves the article's argument without presenting its conclusions as independently established results.
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The source scans remain the record. This page preserves the periodical's argument and reported observations without presenting its conclusions as independently established results. The claims remain attributed to The Flaming Sword.
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The Flaming Sword · Vol. 14, No. 3 · 8 Dec 1899 · PDF p. 11