
Theodolite used for the Principal Triangulation of Great Britain
1791
1791
1794
circa 1800
1798
1797
circa 1805
1791
1800
1805
1790
1796
1800
1794
1800
1800
1800
1795-1805
1792
1795
1800
1790
1802
1795
1795
1790
1792
1802
1790
1799-1802
1797-1804
1793-1803
1795-1805 (original)
1799
1805
1796-1798
1796-1797
1802
1893-4
1795
1792
2000-100 BCE
1795-1805
1790
1990-96
1800
1791
1790-1794
1804
1799
1795-1805