In certain situations - near waterfalls, where the sea breaks onto rocks, in pine forests, mountain areas and following lightning storms, you may notice you feel invigorated and refreshed, because you've been breathing air with a high content of small negative ions of oxygen.

Positive ions are the witches that ride dry winds, inhabit modern buildings, multiply in the toxic canyons of the cities, lurk in our homes and bottle up in closed motor cars.

The so-called 'witch's winds' are winds called the Foehn in Switzerland, Sharav in the Middle East, the Mistral in France, the Sirocco in Italy, California's Santa Ana, Sydney and Brisbane's Westerlies, Melbourne's Northerlies, Perth's Easterlies and Adelaide's Northerlies - all have long been traditionally blamed for causing illness, accidents and depression.