Tides, Weather and Climates, Humidity, Temperature, Seven Wonders of the Ancient World, Seven Wonders of the Medieval World

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  • Tides are caused by the gravitational attraction - the ‘pull’ of the moon on the earth, sometimes assisted by and sometimes hindered by the Sun.
  • At new and full moon, when the Sun, Moon and Earth are practically in a straight line the attractive force of the Sun increases that of the Moon. Such high tides are called spring tides.

Weather and Climates

  • Weather may be defined as the condition of the atmosphere at any place at a particular time. The average weather conditions determine the climate.
  • Humidity, temperature, elevation, distance from the sea, ocean currents, atmosphere pressure and prevailing winds combine to affect the climate of a region.


  • Humidity, the term used to express the dampness of the atmosphere, is due to the pressure of water vapour. Evaporation is the mean by which water is drawn off as invisible water vapour from oceans, lakes, rivers, etc. , when the air contains as much water vapour as it can hold is said to be saturated. When saturated air is cooled, condensation takes place and some of the water which forms the clouds grows larger, they precipitate i.e.. , fall to the earth as rain. The proportion of water vapour in the air, compared with the maximum it can hold at the same temperature, is known as Relative Humidity.
  • Dew is caused by the condensation of water vapour on the cold ground during the night. The temperature at which such condensation takes place is called the Dew Point. When condensation takes place near the surface (and not on the ground) the result is usually mist or fog. When condensation takes place at some distance from the ground, clouds are formed. When water vapour is condensed at a temperature below freezing point it forms snow.
  • There are various kinds of clouds. The layer like clouds often seen on the horizon at sunrise and sunset are called stratus clouds. The light wispy clouds formed high in the sky are called cirrus clouds. The heaped up clouds, looking rather like masses of cotton wool are called cumulus clouds. The black rain clouds are known as nimbus.


  • Of all climatic factors, temperature is the most important. It affects man՚s food, crops, dress and the type of dwelling he builds. Temperature decreases 1oF for every 300 feet above the sea-level. This decrease is largely due to the fact that the rarefied air, found in elevated regions, absorbs less heat than the denser air at lower levels.

Seven Wonders of the Ancient World

  • The Pyramids of Khufu
  • The Hanging Gardens of Babylon
  • The Temple of Artem is at Ephesus
  • The Statue of Zeus at Olympia
  • The Mausolus at Halicarnassus
  • The Colossus of Rhodes
  • The Paros (Lighthouse) at Alexandria

Seven Wonders of the Medieval World

  • The Coliseum of Rome
  • The Great Wall of China
  • The Porcelain Tower of Nanking, Cahina
  • The Mosque at St. Sophia (Constantinople)
  • The Stonehenge of England
  • The Catacombs of Alexandria
  • The Leaning Tower of Pisa

Seven Natural Wonders of the World

  • Mount Everest, on the border of Tibet and Nepal.
  • The Nile River, Egypt.
  • Rio de Janeiro Harbour.
  • Iguassu Falls, Argentina.
  • Yosemite Valley and the Giant Sequoias of California.
  • The Grand Canyon, Colorado River, Arizona.
  • The Northern Lights, especially from Northern Canada and Alaska.

Seven Wonders of Today

  • The Taj Mahal of Agra, India.
  • The Great Pyramid of Egypt and the adjacent Great Sphinx of Gizeh.
  • Hagias Sophia, 6th Century, in present day Istanbul.
  • Leaning Tower of Pisa, Italy.
  • The Eiffel Tower, Paris.
  • The Washington Monument, Washington.
  • The Empire State Building, New York City.

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