shares of canadian national railway co cnr shed 015 to c15628 tuesday in what proved to be an otherwise allaround positive trading session for the canadian market with the sptsx composite index gsptse rising 017 to 1965753 canadian national railway co closed c1911 short of its 52week high c17539 which the company achieved on december 13th trading volume of 25 m shares eclipsed its 50day average volume of 13 m