![]() ![]() When a displacement occurred, the center of the reticles projected itself on one of the circles or between two concentric circles the number was read and the position on the corresponding sector was noted, which was immediately reported, as nearly as possible, on a paper chart representing the reduced scale pattern.įrom 1893 to 1895, in order to record the displacements due to temperature, observations were made in a more or less regular manner at seven o'clock in the morning, at noon and at seven o'clock in the evening. It had been settled once and for all by calm weather, without sun, and at a temperature of about 10 °, so that the crossing of the threads of the reticle coincided with the center of the sight. ![]() This suitably oriented pattern was observed using a theodolite attached to a solid masonry solid at the base of the East Pillar. These rings were numbered and divided into sectors by the eight divisions of the quadrant. The number of these rings was 10 and their extreme diameter 0.40 m. In order to measure these displacements, a protrusion made of varnished sheet was raised on the terrace of the third platform and on the east coast angle, the lower face of which looked at the eastern pillar bore concentric rings 20 mm wide. ![]() This method, the results of which are given below, is just as reliable as it has been done with great precision. The other method is more complex, it was implemented by the military, it consists in raising the position of the top of the tower by geodesic measurements. This is how we distinguish between the movements due to the temperature and those due to the wind, it is enough to know the weather to deduce the type of movement that we observe. It is an interesting and perfectly reliable method, but one which requires a great regularity in the observations. With time he noticed a shift of the sight, the telescope, it, remaining perfectly fixed. The first was to put a sight overhanging the summit and a telescope at ground level, perfectly fixed on the center of the sight. Usually, it is rather between 4 and 8 cm, as shown in the statements below.įrom the first years after the construction of the tower Gustave Eiffel had measured the movements of the summit, but we can ask how he did it, since at the time he did not have the tools technollogiques that exist our days. Just to say it right away, the biggest deviation ever seen from the top occurred during the storm of 1999, a storm during which the oscillation was 13 cm. On the other hand, the temperature and the wind, yes. All that does not count in moving the top of the Eiffel Tower. The other causes are perfectly negligible: difference in atmospheric pressure, efforts due to vertical winds, disturbances due to the visitors of the tower, all of which would be massed on one side, etc. There may be several causes for this phenomenon, but only two have importance: The temperature, which expands the metal, and the wind, which offers a horizontal force. Although it is metal, the Eiffel Tower oscillates on its base, but of course it is only the summit which in suffer the consequences, it moves slightly in one direction or another. ![]()
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