Zaccarias Janssen

Zacharias Janssen; also Zacharias Jansen or Sacharias Jansen; 1585 – pre-1632 ) was a Dutch spectacle-maker who lived most of his life in Middelburg. He is associated with the invention of the first optical telescope and/or the first truly compound microscope, but these claims (made 20 years after his death) may be fabrications put forward by his son.

Biography Zacharias Janssen was born in The Hague. Local records seem to indicate he was born in 1585 although a date of birth as early as 1580 His parents were Hans Martens (who may have been a peddler) and Maeyken Meertens, both probably from Antwerp, Belgium. He grew up with his sister Sara in Middelburg, at the time the second most important city of the Netherlands. He was known as a "street seller" who was constantly in trouble with the local authorities. The family had to move to Arnemuiden in 1618 after Zacharias's counterfeiting activities were exposed. There Zacharias was again accused of counterfeiting in 1619, causing him to be on the move again, ending up back in Middelburg in 1621.

A year after the death of Janssen's first wife in 1624, he married Anna Couget from Antwerp, who was the widow of a Willem Jansen (probably a relative of Janssen). He moved to Amsterdam in November 1626 with a profession of a spectacle maker, but was bankrupt by 1628. Janssen has been given a death date as late as 1638

The claim that Zacharias Janssen invented the telescope and the microscope dates back to the year 1655. During that time Dutch diplomat Willem Boreel conducted an investigation trying to figure out who invented the telescope. Boreel's conclusion that Zacharias Janssen invented the telescope a little ahead of spectacle maker Hans Lippershey was adopted by Pierre Borel in his 1656 book on the subject.

In Boreel's investigation Johannes also claimed his father, Zacharias Janssen, invented the compound microscope in 1590. For this to be true (Zacharias most likely dates of birth would have made him 2–5 years old at the time) some historians concluded grandfather Hans Martens must have invented it.

Other claims have come forward over the years. Physicist Jean Henri van Swinden's 1822-23 investigation reached the conclusion supporting Janssen and in 1841 a collector named Zacharias Snijder came forward with 4 iron tubes with lenses in them purported to be Janssen original telescopes. In historian Cornelis de Waard's 1906 book on the history of the telescope he recounted his discovery of a note written in 1634 by the Dutch philosopher Isaac Beeckman in which Beeckman mentioned that Johannes Zachariassen claimed his father created his first telescope in 1604 (and that it was a copy of an Italian device from 1590). The German astronomer Simon Marius's account to his patron Johan Philip Fuchs von Bimbach about meeting an unnamed Dutchman at the 1608 Autumn Frankfurt Fair who tried to sell him a device that sounded like a broken telescope has led to later speculation this unnamed Dutchman could have been Zacharias Janssen.

Controversy Reproduction of an optical device that Zacharias Snijder in 1841 claimed was an early telescope built by Jansen. Dutch biologist and naturalist Pieter Harting claimed in 1858 that this was an early microscope which he also attributed to Janssen, perpetuating the Janssen claim to both devices. Its actual function and creator has been disputed.

The confusion surrounding the claim to invention of the telescope and the microscope arises in part from the (sometimes conflicting) testimony of Zacharias Janssen's son, Johannes Zachariassen. Johannes' various claims include that his father invented the telescope in 1590, that his father invented the telescope in 1604, that in 1618 he and his father invented the Keplerian telescope (a design using two positive lenses proposed by Johannes Kepler in 1611), and that (Adriaan) Metius and Cornelis Drebbel bought a telescope from him and his father in 1620 and copied it.

The 1655 investigation by William Boreel (who may have been a childhood friend of Zacharias Zachariassen) added to the confusion over invention. The people he had the local magistrate interview were trying to recount details 50 or 60 years after the fact and Boreel may have confused the names of spectacle makers from his childhood. He may have also been confused about a microscope built by another optician for Drebbel, claiming it was built by Zacharias Janssen.

Albert Van Helden, Sven Dupré, Rob Van Gent, and Huib Zuidervaart in their book "Origins of the Telescope" came to the conclusion that Janssen may not have become an optician until 1616 and that the claims surrounding him as the inventor of the telescope and the microscope were the fabrications of his own son, Johannes Zachariassen, who claimed it as a matter of fame and for possible financial gain.