The proposals for such work and the contracts made with the parties successful in the competition, reserve the right to the Postmaster General to change the values, designs, etc., from time to time as he may judge expedient, and specify nothing as to these particulars, while they are very specific as to the quality of the work, and the precautions to be observed in the manufacture, to prevent pecuniary loss to the Department. A government official inspects the work in order that it may conform in quality to the contract, and the records are kept of the number of stamps of each value made and turned over to the Department, without further specifications. In a word, no record is preserved of how many stamps of any particular design, paper, water-mark, perforation or other peculiarity, are made, or of the date of the adoption of any of these things. Third Assistant Postmaster General Ireland, during his term of office, once wrote "It has always surprised me that the Department has never kept any official history of its stamps." Many of these details might be gathered no doubt from the very voluminous correspondence between the Department and the several contractors, if it were accessible, but upon investigation it appears that many interesting changes have been made upon mere verbal instructions. We shall have therefore to rely upon quite different sources for our information. Fortunately the enterprise of collectors has probably discovered all the varieties of the stamps themselves, and only a careful study of them is necessary to their complete description. The materials upon which the present work is based were gathered together mostly as accident threw them into the hands of the author, from time to time, without any attempt at systematic research or arrangement, until at the request of J. B. Moens, of Brussells, they were arranged to form a volume of his "Bibliotheque Des Timbrophiles." The annual reports of the Postmaster General have furnished some points of interest directly and many inferentially; the circulars notifying postmasters of the more important changes, a nearly complete file of which has been consulted, have been a great guide; while frequently very interesting details have been extracted from the files of contemporaneous daily papers; and the published results of the researches of such indefatigable investigators as Messrs. Bagg, Brown and Scott, in the Philatelical Press, and the articles of Cosmopolitan and Scott have been freely drawn upon. Many large collections have been kindly submitted for inspection, in particular those of Messrs Van Derlip, Sterling and Casey, and thus we are able to describe every stamp and essay from actual specimens, except in a few instances specially noted. While there may be possible omissions, the reader may feel assured of the existence of everything described.