The duo had a falling out during this project, and the quality of the telescopes suffered. The Leiden telescope, finished in 1821 was so bad that it was sold as scrap in 1845. The telescope for Utrecht was never installed. Roelofs also calculated the times of solar eclipses for Rienks. During the eclipse of 7 September 1820 there were quite a number of people on the farm with Roelofs. His brothers already died some time before. Pieter died in 1801, and Albert in 1809. The governor of Friesland, Idsert Aebinga van Humalda was present. Professors and their work associates from Franeker were there and also Eisinga. Arjen Roelofs observed four transits of Mercury. For three of these he made accurate predictions of the start and end times. His observations did not correspond to the orbital elements that were known at the time. If he had made this better known, a more accurate orbit for Mercury could have been calculated. Arjen Roelofs was too modest. Different projects Arjen Roelofs was also busy with other activities. He developed lightning conductors, and better sea dikes. Farm houses were often struck by lightning. Roelofs studied this by using a kite. He invented a lightning rod. He employed Rienks to make them, and sold them for 30 guilders each. After the flood disaster of 1825, Roelofs worked on dikes. He studied them to see if they could be improved. Roelofs made a proposal to the provincial government to build the dikes differently. Before this the sides of the dikes were steep and protected by wooden posts. These poles had been eaten by shipworm. Roelofs proposed to get rid of the wooden posts, and to have the faces of the dikes more moderately sloped and covered with a sturdy layer of earth. Willem Loré had already thought of this, and it is not known if Roelofs was aware of Loré's ideas. Death The farmer professor died in Hijum at the age of 74 years, after a long illness. He was buried next to his brothers and sister at the grave yard at Hijum. The road from Oude Leije that passes the location of Hommema-sate was renamed Arjen Roelofswei. Also the school at Hijum is named after him. Manuscripts Roelofs could have done better than what he did. His problem was that he was too much of an individualist. He did not use tables, but would rather