shares of canadian national railway co cnr slid 099 to c15915 wednesday in what proved to be an allaround negative trading session for the canadian market with the sptsx composite index gsptse falling 050 to 2010389 canadian national railway co closed c1624 below its 52week high c17539 which the company reached on december 13th trading volume of 808849 shares remained below its 50day average volume of 13 m