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"The theatre was essentially like the Grecian in its arrangement; it formed a semicircle with seats rising in the form of an amphitheatre for the spectators, at the chord of which was the stage, with its permanent decorations."

Ground Plan of the Theatre at Pompeii

"The theatre was essentially like the Grecian in its arrangement; it formed a semicircle with seats…

A diagram illustrating one type of time-limit relay. Diagrammatic drawing of a time-limit circuit breaker.

Time Limit

A diagram illustrating one type of time-limit relay. Diagrammatic drawing of a time-limit circuit breaker.

"The transmitter is a microphone adapted for the transmission of telephone messages and, in general practice, is so used, better results being thus secured than is possible when the transmitter and receiver are identical. In the Blake transmitter, a diagram is supported back of a mouthpiece, as in the Bell telephone."

Blake transmitter

"The transmitter is a microphone adapted for the transmission of telephone messages and, in general…

An early helicopter concept.

Villard's Helicopter

An early helicopter concept.

An illustration showing a "floral diagram of [the' Viola [plant], showing arrangement of parts in horizontal plan. b, pair of bractoeles below the flower; s, sepals; p, petals; st, stamens; o, ovary" (Britannica, 102).

Viola Diagram

An illustration showing a "floral diagram of [the' Viola [plant], showing arrangement of parts in horizontal…

A Watt's work diagram, or indicator diagram, for steam pressure in cylinder. The graph (top) illustrates how the piston will do work on the steam. The curved top portion is the steam expansion.

Watt's Work Indicator Diagram

A Watt's work diagram, or indicator diagram, for steam pressure in cylinder. The graph (top) illustrates…

Diagram showing the development of the breaking wave and the "swash" after breaking.

Breaking Wave Diagram

Diagram showing the development of the breaking wave and the "swash" after breaking.

"Diagram indicating one explanation which has been advanced for light and heat waves generated by the movement of an electron around its orbit in a molecule and by the simultaneous movement of the molecule." —Croft 1917

Light Waves

"Diagram indicating one explanation which has been advanced for light and heat waves generated by the…

Diagram illustrating the relation of the Dansville to the Wayland Valleys. The floor of the Wayland Valley at Wayland has an elevation of 1372 feet. Its continuation on the extreme left hand of the diagram is 1300 feet. The elevation of the Dansville Valley at Dansville is 700 feet. Both valleys are partially filled by drift. The streams which dissect the Wayland Valley have cut narrow gorges in the rock bottom.

Wayland Valleys

Diagram illustrating the relation of the Dansville to the Wayland Valleys. The floor of the Wayland…