by Barkham Burroughs
Available in 217 free installments
Owner:
LEANING TOWER OF PISA.--The leaning tower of Pisa was commenced in 1152, and was not finished till the fourteenth century. Tho cathedral to which this belongs was erected to celebrate a triumph of the Pisans in the harbor of Palermo in 1063, when allied with the Normans to drive the Saracens out of Sicily. It is a circular building, one hundred feet in diameter and 179 feet in extreme height, and has fine mosaic pavements, elaborately carved columns, and numerous bas-reliefs. The building is of white marble. The tower is divided into eight stories, each having an outside gallery of seven feet projection, and the topmost story overhangs the base about sixteen feet, though, as the center of gravity is still ten feet within the base, the building is perfectly safe. It has been supposed that this inclination was intentional, but the opinion that the foundation has sunk is no doubt correct. It is most likely that the defective foundation became perceptible before the tower had reached one-half its height, as at that elevation the unequal length of the columns exhibits an endeavor to restore the perpendicular, and at about the same place the walls are strengthened with iron bars.
What causes the water to flow out of an artesian well?--The theoretical explanation of the phenomenon is easily understood. The secondary and tertiary geological formations often present the appearance of immense basins, the boundary or rim of the basin having been formed by an upheaval of adjacent strata. In these formations it often happens that a porous stratum, consisting of sand, sandstone, chalk or other calcareous matter, is included between two impermeable layers of clay, so as to form a flat [Transcriber's Note: The original text reads 'porus'] porous U tube, continuous from side to side of the valley, the outcrop on the surrounding hills forming the mouth of the tube. The rain filtering down through the porous layer to the bottom of the basin forms there a subterranean pool, which, with the liquid or semi-liquid column pressing upon it, constitutes a sort of huge natural hydrostatic bellows. Sometimes the pressure on the superincumbent crust is so great as to cause an upheaval or disturbance of the valley. It is obvious, then, that when a hole is bored down through the upper impermeable layer to the surface of the lake, the water will be forced up by the natural law of water seeking its level to a height above the surface of the valley, greater or less, according to the elevation of the level in the feeding column, thus forming a natural mountain on precisely the same principle as that of most artificial fountains, where the water supply comes from a considerable height above the jet.
HOW MANY CUBIC FEET THERE ARE IN A TON OF COAL.--There is a difference between a ton of hard coal and one of soft coal. For that matter, coal from different mines, whether hard or soft, differs in weight, and consequently in cubic measure, according to quality. Then there is a difference according to size. To illustrate, careful measurements have been made of Wilkes-barre anthracite, a fine quality of hard coal, with the following results:
Cubic-feet Cubic feet in ton of in ton of Size of coal. 2,240 lbs. 2,000 lbs.
Lump 33.2 28.8 Broken 33.9 30.3 Egg 34.5 30.8 Stone 34.8 31.1 Chestnut
