Paul Vasarhelyi

* Szepesolaszi, March 25, 1795 – † Buda, April 8, 1846 / hydraulic engineer, member of the Hungarian Academy of Sciences (1838) ; ; He completed his secondary school studies in Miskolc and Prešov. He received his diploma in 1816 at the Engineering Institute of the University of Pest, where he studied geodesy with György Schmidt (1765–1838), physics and the basics of water regulation with Ádám Tomcsányi (Kálmánfalva), among others. He began working alongside Mátyás Huszár (Kisheresztény) at the Körös survey in 1819. From 1823, he was also a colleague of Huszár in the Danube survey, and from 1829, he was the head of the works. Under his direction, the survey of the section of the Danube between Pétervárad and Orsova and the map of the most difficult section of the Danube were made (1832–1834). From 1833, under the direction of István Széchenyi as the Royal Commissioner for Danube Regulation, he prepared the plan for the regulation of the Iron Gate in the Danube, and then began the construction of the sub-Danube road (1834–1835), later named after Széchenyi, and the regulation of the Iron Gate (1834–1837), which he did not manage to complete due to the withdrawal of government support. (The regulation of the Iron Gate on the Danube, based on his surveys and modernized plans, was only implemented by the Hungarian government well after the compromise, between 1889 and 1896.) Meanwhile, in 1833 and 1834, he went on a long study trip to Western Europe (England and Ireland) with Széchenyi in order to acquire the necessary equipment for the regulation. In 1837, he was assigned to the Buda headquarters of the Directorate of Water and Architecture as a first navigation engineer, and from 1841 he participated in the control and management of water works in various parts of the country as a central navigation inspector. During the Pest flood disaster of 1838, he and his colleagues took surveys of the situation of ice dams. Based on his in-depth knowledge of the water conditions of the Budapest section of the Danube, he published his study on the subject of the Budapest Standing Bridge in the Athenaeum in the 1838 issue, which, contrary to the opinions of laymen who feared another glacial flood in Pest, presented scientific arguments in favor of building the Chain Bridge. In 1843, he prepared one of his most important works, the determination of the height of the Danube and its tributaries relative to the level of the Adriatic Sea (Case Study Map of Hungary... az Adriatenger ; apósitás a térképe). With this map, he implemented a uniform national base level relative to the level of the Adriatic for the first time. ; With the help of the national base level, it was possible to determine the actual height conditions of the country for the first time. After that, in technical practice, the heights obtained in hydrographic leveling and relative to the level of the Adriatic Sea were called Vásárhelyi heights. His main work is the Tisza regulation plan, which he developed based on the data of the Tisza survey conducted between 1833 and 1845 under the leadership of Sámuel Lányi and using the detailed regulation plans prepared during this period. He submitted his Preliminary Proposal for the regulation of the upper reaches of the Tisza on 8 June 1845, and after the basic principles of the regulation were accepted, he also submitted the General Regulation of the Tisza River… plan on 25 March 1846. According to this principle, river regulation and flood relief should be treated as a single task, and in order to accelerate the retreat of floods, the length of the river should be shortened by cuttings. The costly plan provoked heated debates at the meeting of the board of the Tisza Valley Society, during which – while defending his plan – he suffered a heart attack and died. The differing opinions of the foreign expert Pietro Paleocapa (1789–1867), who was invited after his death, had a detrimental effect on the planned nature of the works that had begun. Their revision necessitated a gradual return to the Vásárhelyi plan, and the regulation of the Tisza was ultimately carried out entirely on the basis of Pál Vásárhelyi's ideas. ; He had already recognized that one of the world's most extensive and richest mineral water resources and hydrothermal energy resources lay untapped beneath the Great Plain. He urged the exploration of the surface and underground waters of the Great Plain. Several of his studies, some in manuscript and some published in print, have survived (triangulation and leveling instructions, river regulation plans, hydraulic measurements, etc.). The most significant of these are the mathematical formula giving the average speed of rivers in a certain cross-section, and his academic chair thesis on the regulation of the Berettyó. The Hungarian Academy of Sciences elected him a corresponding member in 1835, and a full member in 1838. ; ; His main works: ; Introductio in praxim triangulationis, 1827, ; On the subject of the Budapest-Pest fixed bridge, 1838, ; Some warning words on the Iron Gate affair, 1838, ; On the degree of velocity in rivers, enlightened by a cross-section measured on the Danube and the velocities found therein (Annual of the Hungarian Scientific Society), 1845.