| 21. | A heliograph was installed in 1879 at Signal Hill, the small rise overlooking the main settlement in Thomson Bay.
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| 22. | A single circuit submarine communications cable was laid from Cottesloe in 1900, after which the heliograph service was discontinued.
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| 23. | Shortly thereafter, the heliograph system was abandoned along with a number of forts used in the Apache campaign ."
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| 24. | During daylight hours when the sun is visible, a heliograph mirror can be used to flash bright, intense sunlight.
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| 25. | During this campaign, Miles's special signals unit used the heliograph extensively, proving its worth in the field.
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| 26. | The primary types of visual signalling were Semaphore flags, lamps and flags, lamps and lights, and the heliograph.
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| 27. | The Baroness rides to a deserted country road, where she uses a heliograph to signal for Filibus's airship.
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| 28. | With Pawsey's help, ?30, 000 was raised from the Ford Foundation to build the Culgoora radio-heliograph.
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| 29. | In the Boer War, where both sides used heliographs, tubes were sometimes used to decrease the dispersion of the beam.
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| 30. | The distance that heliograph signals could be seen depended on the clarity of the sky and the size of the mirrors used.
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