The ancient battering ram was of massive timber, 60 to 100 feet long, fitted with an iron head.  It was erected under shelter to protect the 60 or 100 men required to work it.  The largest was equal in force to a 36-lb. shot from a cannon.

Pile Driving on Sandy Soils.—­The greatest force will not effect a penetration exceeding 15 feet.

Various Sizes of Type.—­It requires 205 lines of Diamond type to make 12 inches, of Pearl 178, of Ruby 166, of Nonpareil 143, of Minion 128, of Brevier 112-1/2, of Bourgeois 102-1/2, of Long Primer 89, of Small Pica 83, of Pica 71-1/2, of English 64.

Wire ropes for the transmission of power vary in size from 3/8 to 7/8 inch diam.  For from 3 to 300 horse power; to promote flexibility, the rope, made of iron, steel, or copper wire, as may be preferred, is provided with a core of hemp, and the speed is 1 mile per minute, more or less, as desired.  Tho rope should run on a well-balanced, grooved, cast iron wheel, of from 4 to 15 feet diam., according as the transmitted power ranges from 3 to 300 horse; the groove should be well cushioned with soft material, as leather or rubber, for the formation of a durable bed for the rope.  With good care the rope will last from 3 to 5 years.

Cannon balls go furthest at an elevation of 30 degrees, and less as the balls are less; the range is furthest when fired from west to east in the direction of the earth’s motion, which for the diurnal rotation on its axis, is at the rate of 1,037 miles per hour, and in its orbit, 66,092 miles.

The air’s resistance is such that a cannon ball of 3 lbs. weight, diameter, 2.78 ins.  Moving with a velocity of 1,800 feet per second, is resisted by a force equal to 156 lbs.

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.