As students and residents of the town wearily slogged through an unusually snowy winter, impatience with continually slushy streets grew stronger and stronger. Some blamed atomic explosions for disrupting the weather. Others felt that either Senator Bridges or the lack of a decent winter holiday had something to do with the general discomfort. Many, however, seemed to think that Mayor Sullivan might have provided snowplows. At any rate, pussy willows are being sold along Mass. Ave., and the trial by wet ankles is obviously over. As galoshes are put away for another occasion, a few may be willing to agree with the traditional Cambridge snow policy, set by Mayor Quinn many years ago. "God brought it," said the good mayor. "Let God take it away."