[150] _Head-office_ is the official term given to the independent post-towns, and such as are only subordinate to one of the three metropolitan offices. _Sub-offices_ are, of course, under the head-offices. _Receiving-offices_, at which letters are received, but not delivered, are also under the authority of the head-office of the neighbourhood. Those post-offices at which money-orders are issued and paid are designated _Money-order Offices_, and include all the head-offices and a large number of sub-offices, and a few receiving-offices. _Packet-Offices_ are those at which the regular mail-packets (ship-letters may be received or despatched. at any port) are received and from which they are despatched. London and Southampton are packet-offices for the Continental Mails, the East and West Indies, and South America. Liverpool, and Queenstown take the United States and Canada. The mail-packets for the Cape of Good Hope and the West Coast of Africa sail to and from Devonport. [151] For further information respecting these offices, see Appendix (D), _Revenue Estimates_; also, for a statement of the amount of postage collected in our largest towns, see Appendix (E). [152] The staff of the largest provincial offices usually consists of clerks, sorters, stampers, messengers, letter-carriers, and rural post-messengers. The _clerks_ are now principally engaged on clerical duties, attending to the public on money-order business, &c. or in connexion with registered letters or unpaid-letter accounts. In offices where the staff is smaller, the clerks also engage in sorting and despatching letters. In many small country towns females are employed as clerks. The _sorters_ are principally engaged in sorting duties. _Stampers_ and _messengers_ do duties such as their designations denote. _Letter-carriers_--the familiar "postmen" of every household--are almost exclusively engaged in delivering letters, &c. from door to door. _Auxiliary letter-carriers_ are those only partially so employed, principally on the largest, or early morning delivery. _Rural post-messengers_ is the official name for "country postmen," who make daily journeys among the villages and hamlets surrounding each town, delivering and taking up letters on their way.