IELTS Reading: Diagram Label Completion (Practice with Answers)

Rainwater was the only reliable water a castle keep possessed, and its collection began invisibly, in the lead sheeting laid over the great hall's roof. Rain ran off the sheets into stone channels running along the eaves, and the channels emptied into carved heads set at each corner of the building, the grotesque figures whose open mouths spouted water clear of the walls.

From the mouths the water fell into lead cisterns set against the base of the keep, and from the cisterns it was carried by elm pipes into a storage tank cut into the rock beneath the basement. The tank, vaulted and lined with mortar, held the winter's accumulation, and a well shaft rose from its cover to the ground floor, where a windlass and bucket served the kitchen. Overflow from the tank drained through a filter of gravel and charcoal into a soakaway at the foot of the motte, protecting the foundations from the water that would otherwise have pooled.

Archaeologists reconstructing such systems note their weak point: the lead sheeting, easily stripped during sieges and expensive to replace, so many keeps survived with a patched roof and a permanent shortage. The elaborate apparatus, one excavator concluded, told the owner's visitors that water could be made to obey even here, on a hill chosen precisely because it had no spring.

A violin looks like a shaped box and behaves like a loudspeaker. The strings, stretched from the tailpiece over the bridge to the pegbox, supply almost no sound themselves. What they supply is energy, transmitted through the bridge into the body, whose thin wooden plates amplify it a thousandfold.

The bridge is not a passive post. Its feet stand on the top plate either side of a small wooden rod, the sound post, wedged vertically between the plates just behind the bridge's treble foot. The post transmits vibration directly to the back plate and, by bracing the top, defines the area that moves. On the bass side, opposite the post, a long flat strip of wood, the bass bar, is glued along the underside of the top plate, stiffening it so the lower strings drive the plate evenly rather than collapsing it at one point.

The two f-holes, the shaped openings flanking the bridge, vent the air inside the body, letting the enclosed air mass resonate as a Helmholtz resonator, the mechanism that gives the instrument its response on the lowest notes. Inside, the volume is everything: plate thickness, graduation from centre to edge, and the exact placement of post and bar are what a maker tunes by hand, tapping and listening, to voice an instrument no two of which are identical.

A limestone cave is a slow argument between water and rock, and every shape inside records a stage of it.

Rain absorbs carbon dioxide from air and soil, turning weakly acidic, and the acid dissolves limestone along joints and bedding planes, enlarging cracks into passages over millions of years. Where such water, saturated with dissolved mineral, drips from a cave ceiling, each drop deposits a ring of calcite, and rings accumulating over millennia build a stalactite, an icicle of stone growing downward. Drops landing beneath build the matching upward spike, a stalagmite, and where the two meet after further growth they form a column.

Flowing water carves the rest. A passage's flat floor is often a former stream bed; undercut walls record the water level when the cave was younger and wetter. Rimstone pools, terraced basins dammed by mineral deposits, hold water on gentle gradients, and where a cave intersects the surface a shaft opens, admitting daylight and, eventually, plants and animals, the caves' colonists arriving by the same door geology left open.