Along with corporate scandals and painful losses, the summer on Wall Street has been one of unusual volatility.

Orders to buy or sell large amounts of stocks are expected, which could create unusual volatility in the market.

The unusual high volatility of the metal compound nickel tetracarbonyl led Kelvin with the statement that Mond had "given wings to the metals'.

Together with the introduction of the floor and ceiling trading limits, the SET also implemented a circuit breaker system to ease any unusual volatility in the market that may cause investor panic.

Instead, the story this week has been of the market's changing moods as investors have been whipsawed by unusual volatility.

Even before the Irish situation hit the headlines, however, we were seeing unusual volatility in on the foreign currency exchanges.

The unusual volatility may have been a function of thin market conditions because of the May Day holiday in Europe.

Given these challenges, concerns linger about whether trading can possibly be smooth on what may prove to be a very heavy day of buying and selling with unusual volatility.

The resulting crisis became acute in September 2008, ushering in a period of unusual volatility, encompassing record 100-point moves in both directions and reaching the highest levels since 1929.

But trading remained extremely thin and nervous, as the unusual volatility of the past week left many institutions shaken.