Bricklayers ascend ladders with loads of 90 lbs., 1 foot per second. There are 484 bricks in a cubic yard, and 4,356 in a rod.
A power of 250 tons is necessary to start a vessel weighing 3,000 tons over greased slides on a marine railway, when in motion, 150 tons only is required.
A modern dredging machine, 123 ft. long, beam 26 ft., breadth over all, 11 ft., will raise 180 tons of mud and clay per hour, 11 feet from water-line.
In tanning, 4 lbs. of oak bark make 1 lb. of leather.
Flame is quenched in air containing 3 per cent, of carbonic acid; the same percentage is fatal to animal life.
100 parts of oak make nearly 23 of charcoal; beech 21, deal 19, apple 23.7, elm 23, ash 25, birch 24, maple 22.8, willow 18, poplar 20, red pine 22.10, white pine 23. The charcoal used in gunpowder is made from willow, alder, and a few other woods. The charred timber found in the ruins of Herculaneum has undergone no change in 1,800 years.
Four volumes of nitrogen and one of oxygen compose atmospheric air in all localities on the globe.
Air extracted from pure water, under an air pump, contains 34.8 per cent. of oxygen. Fish breathe this air, respiring about 35 times per minute. The oxhydrogen lime light may be seen from mountains at the distance of 200 miles round.
Lightning is reflected 150 to 200 miles.