
Theodolite used for the Principal Triangulation of Great Britain
1791
1791
1794
circa 1800
1798
1797
1791
1800
1790
1796
1800
1794
1800
1800
1800
1792
1795
1800
1790
1802
1795
1795
1790
1792
1802
1790
1799-1802
1797-1804
1793-1803
1799
1796-1798
1796-1797
1802
1893-4
1795
1792
2000-100 BCE
1790
1990-96
1800
1791
1790-1794
1804
1799
1795
1800
circa 1801
1797
1799
circa 1795
circa 1800