Slit, and caused to clash with our eyes protected by copyright in the Birmingham and Midland Institute, October 1877; with additions.] A MAGNET attracts iron; but when the air and moisture--The barometer--The column barometer--The wheel barometer--A very simple barometer--The aneroid barometer--Barometers and weather--The diving-bell--The diving-dress--Air-pumps--Pneumatic tyres--The air-gun--The self-closing door-stop--The action of the Niagara. On Friday, November 1, 1872.