Electric hygrometer element in sealed glass tube
1944
1944
1960-1970
1941
1851-1900
1894
1898
1895-1909 (estimated)
1875-1885
1899
1894
1882-1909 (estimated)
1926, April
1882, Nov 6
1939
1941
1941
1939
2003-2006
1998
1985
1890
1939
1934