Telegraph block instrument; South Eastern Railway; Walker's patent No. 245
1855
1855
1850
1860-1920
1938; (1838)
1853
1853
1852
1852
1853
2000-100 BCE
1834-1836
1854
circa 1854
circa 1854
1855
1850
1934
1893-4
1850
1852
1610; 1923
1850
1851
1851
1855
1856
1854
1863-7
1850
1850
1851
1850-1856
1955; 1830
1855
1852
1851
1854
1854
1772 (original); 1919 (model)
1801-1840 (original); 1901 (model)
1775-1799 (original); 1900-1907 (model)
4000-2001 BCE
1850
circa 1850s
1839 (original); circa 1988 (replica)
1990-96
1853
1851
circa 1854
1851