As the day slipped quickly away and twilight settled on Cecil County on this busy last weekend before Christmas, the lights of the Conowingo Dam flickered to life. In contrast to the frenzied day of last-minute shopping in downtowns and malls, the scene on the Susquehanna was quiet and settled this Saturday evening at this old river crossing. Reflecting from the lake, a colorful array of lights glowed softly in the gathering darkness as people settled in for the longest night of the year. The northwestern crossing from Cecil to Harford counties has always been an important one and earlier bridges made way for the Conowingo Dam, which opened in 1928.