1891 in science

Mars-crossing asteroid

in set theory, the theorem that a set has a strictly smaller cardinality than its powerset

projection formula in which vertically drawn bonds are considered to lie below the projection plane and horizontal bonds to lie above that plane

thumb|North American taximeter thumb|Indonesian taximeter thumb|Japanese taximeter thumb|Serbian taximeter

overview of natural science-related events during the year of 1891

1891 trade show in Frankfurt am Main, Germany

Otto Lilienthal's glider