The deputy for Culture, César Augusto Asencio, presided over the presentation this morning at the MARQ of a replica of the Thomson Tide Gauge which from now on will occupy a preferential place in one of the museum's rooms. The piece, on loan from the National Geographic Institute (ING), is an exact copy of the original which even today continues to collect data, in a testimonial manner, from the Port of Alicante.
Asencio stressed that thanks to this initiative "we can recall the history and highlight the value of a device that has been fundamental for Alicante as the origin of the Cota 0 and, consequently, as the basis for the preparation of the National Topographic Map". The event was also attended by Marcelino Valdés, head of the Geodesy area of the ING, José Miguel Saval, sub-delegate of the Government, José Alberto Cortés, managing director of the MARQ Foundation, Manuel Olcina, technical director of the MARQ and Ignacio Hernández, the topographer commissioner of the tide gauge and head of New Technologies of the MARQ.
A tide gauge is a device with a clockwork mechanism that records variations in sea level and establishes an average level at a certain place and for a certain period. In 1926, the model of Sir William Thomson, Lord Kelvin, a British engineer, mathematician and physicist who profoundly influenced the scientific thinking of his generation and developed the Kelvin temperature scale, was installed in the Port of Alicante. The piece, which was operational until 1969, was built by the London firm Negretti & Zambrana and in 1949 the "Maquinista Valenciana" made three replicas, one of which is the one on display today at the MARQ.
In 1870, the mean sea level in Alicante was adopted as the reference plane for the establishment of 'Cota 0' from which to start measuring and giving altitudes to the Geodetic Network and, consequently, to the National Topographic Map. The choice of Alicante as the fundamental reference point was based on the characteristics of the Mediterranean Sea in the Alicante bay, its unbeatable climatic and meteorological conditions and, above all, the important railway infrastructure which, in 1858, brought the Madrid-Alicante line into operation.
In order to establish this 'Cota 0', an official observed the sea level four times a day (at 9:00, 12:00, 15:00 and 18:00 hours), for almost four years, on a metal strip located on a staircase of the Muelle de Levante in the Port of Alicante. With the observations made, he placed a bronze disc with the inscription "NP-1" - Precision Level number 1 - on the first step of the main entrance to Alicante City Hall. This disc, which shows that the step is 3.407 metres above the zero level of the Port, has been used as the national altimetric reference by the Geodesic Network to draw up the cartography of Spain.
Between 1871 and 1872 the levelling line between Alicante and Madrid was completed along the railway line linking the two towns and from then on the altitude routes taken from the Port were extended to all corners of the peninsula.
In 1874 the observations on the tide rule were interrupted and measurements began on the first tide gauge, designed by Adie, which worked in Spain and which was operational until 1924. In 1926, the Thomson tide gauge was installed in the tide gauge station, built on the outer breakwater of the Levante seawall, and it continues to collect data even today, although only in a testimonial way.
