On June 16, 1754, the birth of the second son of its leading physician wasregistered in the "Militärmatriken" of the Invalides' Hospital at Pest,Hungary. The father was Joseph Zach from Olmütz and the mother Clara née Sontag.The son received the name Joannes Franciscus Xaverius Vitus Fridericus, andlater became a geodesist and astronomer. For these professions, he acted around1800 not only as a kind of international information centre, but he moreoverstimulated the work of the other colleagues and carried out importantobservations and reductions. He studied and published historical sources, andhis journals constitute themselves more an ocean than a source of the historyof our science, an ocean which is still to be explored for as yet undetectedislands.At the occasion of the 250 birthday of Franz Xaver von Zach, Hungariancolleagues took the initiative to commemorate him by a symposium at the seat ofthe Hungarian Academy of Sciences. This book contains contributions that arebased on lectures given at the Budapest symposium "The European Scientist".