The doctrine of res ipsa loquitur does not apply to the instant case, there being no inference of negligence arising from the mere slipping on the Post Office floor. It, therefore, was incumbent upon the plaintiff to establish the negligence of the defendant. Bowser v. J. C. Penny Co., 354 Pa. 1, 40 A.2d 324. To establish negligence, plaintiff would have to have shown that the defendant had (1) actual knowledge of the existence of this puddle of slush; or (2) that the puddle had existed for a sufficient time prior to the accident, and thus charge the defendant with notice of its existence. There is no evidence to support either of these positions.