To trace the course and source of a river is a simple task through the work of modern geographers, and such a pursuit illustrates well the two methods here considered, but it is doubtful if any river was ever traced originally from its fountain head to its mouth. The backward way of such exploration, from the nature of the case, has always been taken, and men have traced the more or less finished products of the lower stretches, backward, still backwards, even as in the Indus, to the still-unknown. The earliest thinkers and seekers in the plains of Bengal were familiar with much of their great sacred and composite river as it flowed into its delta. Slowly, laboriously, here a little and there a little, they learned its stupendous story. They found the plateau of Tibet in the Himalayas where the twin-sisters, Brahmaputra and Ganges were born, and saw how from the one high cradle they parted on their eastward course for a thousand miles with the mountain-chain between them, and how, coming together again, the one descending through Assam and the other flowing through the plains, reinforced by the Jumna, they united to form the Ganges-Brahmaputra. A great subject indeed for the early geographer, but one which he could only follow in the backward way. Again how well known and revered in Egypt was the Nile for thousands of years before its source in Victoria Nyanza could be traced, even though Nero might send his explorers as far as the marshes of the White Nile, and Ptolemy’s search for it might lead him to guess the riddle, and assign it to two great lakes! Genealogy. Not many of us can trace our ancestry in the direct male line to the 8th century by authentic and written documents as did a Hebrew friend of mine, thus effectually meeting the doubts of a prospective brother-in-law who asked him as to his fitness to enter a family which was able to produce a stray peer of the realm in its roll. On the other hand a man who has lost his parents in childhood may know nothing of them but that his father’s name was A. Mann, and that he was buried in a Kentish churchyard. He may go on a pilgrimage and find there recorded the fact that A. Mann was the son of A. Mann, Gent, who came from Northumberland. He will doubtless make another pilgrimage and find there a large vault, and over it an imposing record of many a Mann, and yet further he may go, and from the Heralds’ College find out the still earlier derivation of his ancestors. Detection of a Crime.