An accident, which had nearly proved fatal to a fine little boy, occurred yesterday afternoon at that part of the Serpentine river where the late Lord Rivers lost his life a short time ago, and which, from the open unprotected state that it is left in, must be always liable to lead to similar disasters. The poor little fellow to whom the accident happened was playing at battledore and shuttlecock with a boy about his own age, and in his thoughtless anxiety to catch the shuttlecock before it fell, he actually ran over the bank into the river and was out of sight in a moment. A foreign gentleman, who was passing near the spot at the time, very humanely plunged into the water after him, and with the assistance of a large Newfoundland dog which he had with him, very speedily saved the boy from a watery grave.