The Passenger Pigeon (Ectopistes migratorius) became extinct as the last surviving bird of the colorful native American species of dove died at the Cincinnati Zoo. The passenger pigeon was hunted to extinction; the fact that it traveled and nested in large flocks made it easy to slaughter. The adult male passenger pigeon had grey upper parts, the tips of the wings and the tail were black; its throat was a dark rust, while its breast was a lighter rust; its eyes were red. The adult female was of a duller color, with brownish upper parts and a lighter, brownish throat and breast; its eyes were black.

In a Presidential Address to the British Association, at York, Sir William Thomson (Lord Kelvin) spoke On the Sources of Energy in Nature Available to Man for the Production of Mechanical Effect. He summarized the natural sources of energy as Tides, Food, Fuel, Wind, and Rain. All except the tides derive energy from the sun. “Heat radiated from the sun ... is the principal source of mechanical effect available to man.” He referred to tide mills, and the possibility of storing energy in batteries between tides, but nevertheless considered the economics impractical for wide application. Windpower he considered “decadent,” but acknowledged coal would become an exhausted resource, thus windmills should generate electrical power. Kelvin also outlined the economics of hydroelectricity.