The Earth: Its Shape, Size, Weight and SpinUniversity Press, 1922 - 141 pagine |
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angle apparatus attracted masses attracting spheres axis base-line beam body bulge calculated Cavendish Cavendish experiment centre of gravity circles round clock common centre deflection diameter direction disc distance due north Earth and Moon earth-pull Earth's surface effect equal equator equatorial exactly experiment feet fixed stars flat Earth force friction George Darwin globe greater gyroscope inch latitude length Let us suppose Lough Foyle M₁ mean density measured ment meridian method million Moon Moon's motion mountain move round nearer nearly Newton observed once in 24 opposite orbit Ordnance Survey pans pendulum perpendicular plane plumb line point of Aries pole height pole star position pound proportional pull radius rotation round the Sun Sandwick Schiehallion seen side sky pole speed spin round station steamer swing telescope temperature theodolite tilt torsion balance torsion rod triangle velocity vertical vibration weight wind wire zenith
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Pagina 78 - the attraction of M on the beam and suspending wires is the same as before, so that the difference of attraction on A and B in the two positions is due to the difference in distance of A and B only, and thus the attraction on the beam,
Pagina 59 - will show how the observations gave the attraction due to the hill. Let us for the moment leave out of account the curvature of the Earth, and suppose it flat. Further, let us suppose that a star is being observed which would be directly overhead if no mountain existed. Then evidently at S. the plumb line is pulled to the
Pagina 61 - about 55", so that the effect of the mountain, the difference between these, was about 12". The next thing was to find the form of the mountain. This was before the days of the Ordnance Survey, so that a
Pagina 59 - After about a month's work at this station, the observatory was moved to the north station and again the same stars were observed with the zenith sector. Another month's work completed this part of the experiment. Fig.
Pagina 56 - away their tent The cold was intense, and so hindered the working of their instruments that they had to apply fire to the levelling screws before they could turn them. Still, they made their observations,
Pagina 61 - times as dense as the mountain. From pieces of the rock of which the mountain is composed, its density was estimated as 2^ times that of water. The Earth should have, therefore, density
Pagina 60 - But the curvature of the Earth also deflects the verticals at N. and S., and in the same way, so that the observed shift of the star is partly due to the mountain, and partly due to the curvature of the Earth. A careful measure was made of the distance between the two stations, and this gave the curvature deflection as about 43". The observed deflection was
Pagina 61 - An exactly similar experiment was made eighty years later, on the completion of the Ordnance Survey of the kingdom. Certain anomalies in the direction of the vertical at Edinburgh led Colonel James, the director, to repeat the Schiehallion experiment, using Arthur's Seat as the deflecting mountain. The value obtained for the mean density of the Earth was about 5£.
Pagina 56 - They were exposed to the full force of the wind which filled their eyes with sand and was continually on the point of