Demainbray's convex lens
1750
1750
circa 1750
1742
2000-100 BCE
1705-1737
1725
1735-1745
1745
1730
1990-96
4000-2001 BCE
1725
1725
1730-1750
1725
10000-5000 BCE
1910-130
1730-1736
1740
1744
1736-1740
1740
1713-1750
1750
1738
1730
1745
1730
1737-1738
1750
1743
1737
1732
1747
1750
1740
1750
1746
1692-1730
1730
1730
1737
1940-1050
1746
1748
1747
1748
1736
8500-2000 BCE
5000-500 BCE