foreign members. Czar Peter met him in Amsterdam and offered him the chair of mathematics in St Petersburg. Hartsoeker did not accept, but the czar did finance an observatory for him in Amsterdam. Later, in 1704, Hartsoeker accepted the offer of Johann Wilhelm, Elector Palatine to become "first mathematician and honorary professor of philosophy" at the University of Heidelberg. The last years of his life were spent in Utrecht. Major works Conjectures physiques, Amsterdam, 1706. Suite des conjectures physiques, Amsterdam, 1708. Eclaircissements sur les conjectures physiques, Amsterdam, 1710. Editions References External links Digitized works by Nicolaas Hartsoeker from the Linda Hall Library (1694) Essay de dioptrique (1696) Principes de physique (1706) Conjectures physiques 1656 births 1725 deaths Dutch biologists 17th-century Dutch inventors 17th-century Dutch mathematicians 18th-century Dutch physicists People from Gouda, South Holland Members of the French Academy of Sciences Members of the Prussian Academy of Sciences Academic staff of Heidelberg University