The losses could not be attributed to misdirection, or any other of the long catalogue of causes not of a criminal nature, though occasioning much alarm and inconvenience. For in the present case the rifled letters had reached the parties addressed. They had been opened, robbed, and resealed. The route over which the letters passed was a long one--some four hundred miles--and the first look at the case seemed almost to forbid the hope of success in its investigation; for it appeared probable that the robber might defy detection as effectually as "a needle in a hay-mow;" and a belief of this kind no doubt encouraged him in his course. There was, however, another fact in connection with the matter, as will presently be seen, of which he was ignorant, which might have caused him at least to hesitate in pursuing his designs, had he known it, for it very much curtailed the limits within which investigation was necessary. The course of the mail on this route was, first to Ogdensburg, some sixty miles, by stage, the mail being overhauled at each of the intermediate offices, eight or ten in number. At Ogdensburg, all matter for New York was put into a "through bag," which was furnished with a brass lock, and not to be opened until its arrival in New York. It may be well here to state that two kinds of locks are used in the mail service; the iron lock for short distances and upon routes where the mails are frequently overhauled, a key to which is in the possession of all the post masters and "Route Agents;" and the brass lock, used for greater safety only between large places and on important routes; the intermediate offices being supplied with their mail matter without the necessity of opening the through bag. Consequently the brass key is in the hands of comparatively few post masters, (only those who are connected with the offices where the through bags are opened,) and of none of the Route Agents. The reader will see from this statement, and others hereafter to be made, that the robberies were probably committed somewhere between the first-mentioned place and Ogdensburg, and that thus it would be necessary to pursue the investigation only on the latter route, some sixty miles as has already been mentioned. The _seals_ of the rifled letters were important witnesses in this case. In the resealing, uncommonly large wafers of a peculiar shade had been used, as well as a particular kind of stamp, which circumstances satisfactorily proved that all the robberies were the handi-work of one person, and probably at a single locality. The letters had in each instance been detained somewhere one day longer than the time usually required for their passage over the route.