Arjen Roelofs

Arjen Roelofs (1 March 1754 - 11 May 1828) was born on the Hommema-sate (estate) near Hijum in Friesland,

Netherlands as the youngest of four sons and two daughters. His father was Roelof Pytters, a tennant farmer and tax

receiver. His mother was Neeltje Alberts from Finkum. The oldest son Klaas trained as a steersman, but did not work as one,

and instead became a doctor in Sexbierum. It was not an easy life on the farm, but this is where the other three boys,

Pieter, Albert and Arjen had to work. Their mother stimulated the interest of the three sons in mathematics, however

their father was unhappy with this.

After their parents had died in 1790, the three brothers took over the farm, and their sister Antje became their housekeeper.

None of these four ever married, and they all lived on the farm until they died.  Arjen Roelofs was supposed to have had 

polio so he could not use his right leg very well, and later he could not work on the farm anymore. This enabled him to

spend more time on his hobbies. Also his brothers joined him in his hobbies. Pieter was known as a mathematician, but was

also an excellent instrument maker. Arjen designed telescopes, and Pieter made them. Albert was a clockmaker. Pieter and

Arjen took meterological measurements and made instruments to accomplish this. They made thermometers, hygrometers,

and measured wind speed and wind direction.

circle of friends

Eise Eisinga regularly spent time at Hijum. He ensured that Franeker University professor Johan Henri van Swinden

became a very regular visitor. Roelofs also took on students. His cousin Roel Hessels Hommema,and his friend Rinse Bearts

Gelder were taught in Hijum. Later Arjen regularly worked with instrument maker and farmer Sieds Johannes Rienks of Hallum.

In 1817 they presented a plan for the construction of a telescope to the Dutch Government. The plan did not eventuate.

However it did interest King Willem I, who named both as Brothers in the Order of the Dutch Lion on 23 September

1817. Roelofs made most of the calculations and measurements for Rienks for the building of the telescopes in Leiden and

Utrecht. Rienks had been commissioned to build these in 1818. 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 ecclipes for Rienks. During the ecclipse of 7 September 1820 there were quite

a number of people on the farmwith Roelofs. His brothers already died sime time before. Pieter died in 1801, and Albert in

1809. The governor of Friesland, Esquire I A 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 betterknown, 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. Arjen 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 eated 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 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 Ajren 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 indivualist. He did not use tables, but would rather calculate everything himself. He also limited himself by being happy to stay in Hijum. He must have written quite a bit by necessity, but he did not ever publish. In 1829 a booklet titled Levensberigten van Arjen Roelofs (Life of Arjen Roelofs) was published by a farmer aquaintance Worp van Peyma from Ternaard. He was able to read Roelofs' hand written notes. Most of these have since been lost. The Eisinga Planetarium has a telescope of Roelofs, and some of his manuscripts. Also the Tresoar in Leeuwarden has a collection.