THE dirt looms large and that means following Dr Dirt himself, astute local trainer Wong Tang-ping. This Wednesday's Sha Tin meeting is split between the grass and the dirt for which Ping's Northern Fire Ball looked on good terms with himself during yesterday's Sha Tin work session. Ping has a brilliant record on the all-weather surface and has been unlucky not to have produced Northern Fire Ball to win on the dirt already this season. Northern Fire Ball has run second twice for his mentor on the dirt, having the decided misfortune to run up against a pair of Patrick Biancone specials in Lucky Charm and Tequila Pop. Last time out, Northern Fire Ball had the others very well beaten off when second to Tequila Pop, who looked nailed on following an extremely promising run prior to his dirt debut and some excellent work. ' In running second, Northern Fire Ball clocked a highly creditable Topspeed figure and should find Wednesday's opposition much more manageable. Yesterday he clocked a more-or-less even 1,200 metres in one minute and 22.7 seconds under stable apprentice Alex Yu. That pipe-opener should leave him primed for action and the one to beat on Wednesday. Geoff Lane's dirt specialist Cruise Cannon was put through his paces yesterday by Douglas Whyte. Cruise Cannon has been working as well as ever for some time and Whyte will be ultra keen for winners, having had to sit and suffer on the sidelines as arch-rival Basil Marcus booted home a four-timer yesterday.