Account of pendulum experiments undertaken in the Harton Colliery, for the purpose of determining the mean density of the earth, by G. B. Airy
my views, and, after the proper surveys for elevation, furnished me with a map extending about 3 miles in all directions round Harton, with the elevations above high water in feet marked at numerous points. I found that a line might be drawn nearly 10 depths distant from <s>[?]</s> the upper station, touching the cliffs of Tynemouth and the cliffs south -east of Harton, and ranging for some distance along the coast of Durham. I therefore drew a line parallel to this at 10 depths distance from the upper station: and divided the whole country into squares (with sides of one depth each) whose sides were parallel and perpendicular to this. These squares I grouped as appeared most convenient as will be seen in the Map, figure 4 (the principal object being to secure a proper representation of Jarrow Slake and the Valley of the Tyne), and adopted for each group the elevation in feet above high water which <s>[?]</s> Mr. Thompson's elevations of special points suggested. <s>[?]</s> The <s>[?]</s> elevation of the upper pendulum station was 74 feet. Consequently the <s>[?]</s> vertical measure which was to be used for computing the "volume" in the formula above was [Elevation - 74]/1256. Of this formula, a small table was prepared. The quantity p was measured graphically from the map, and √[p<sup>2</sup> + 1] was formed graphically from it.
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Account of pendulum experiments undertaken in the Harton Colliery, for the purpose of determining the mean density of the earth, by G. B. Airy, 1855. From The Royal Society, PT/54/5
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