"It came across the low-lying fields as a drifting fog that some men saw as gray, some as yellow, some as green."Thus did Historian Ralph Allen describe the deadly mist of chlorine gas that ravaged the Canadian First Division at Ypres in 1915. Last week, as Canada celebrated Remembrance Daythe 61st anniversary of the end of World War Ifear of another kind of chlorine gas attack forced the evacuation of Mississauga, Ont. (pop. 276,000).
Shortly before midnight on Nov. 10, tankers on a 106-car Canadian Pacific freight train, bound from Windsor to Toronto, jumped the tracks. Three explosions from cars...