
Theodolite used for the Principal Triangulation of Great Britain
1791
1791
1795
1821
1794
1798
1797
1805
1800
1812
1795
circa 1808
1808
1793-1803
circa 1805
1807
1815
1815
1795-1810
1863-7
1791
1808
1800
1807
1821
1790
1796
1794
1800
1800
1800
1795-1805
1807
1812
1792
1795
1800
1790
1807
1814
1802
1795
1795
1816
1790
1792
1792
1802
1790
1799-1802
1790-1810