rance, provision is made for the delivery of letters at
every house in the country, while in the United States and Canada there
is in general no house-to-house delivery in rural districts. Until
recently there was no rural delivery service of any kind in the latter
countries. Letters could be obtained only at the rural post offices. And
the system now being introduced provides only for delivery into roadside
boxes at the points on the rural deliverer's route nearest to the house
of the addressee. Such adjustments, of course, materially affect the
cost and profit of the service.

[637] E.g. the war increases in the United Kingdom and in other
countries. The point is further considered in the Appendix "Post Office
Revenue," _infra_, p. 358 ff.

[638] Graphically, the variation of the number of letters with changes
in the rate of postage would be represented by an asymptotic curve.

[639] It appeared in the English letter rate of 1885, but disappeared
with the changes of 1897. It has been reintroduced into the letter rate
with the war changes of November 1915, and the result is an awkward
scale.

[640] This point is dealt with more fully in connection with the parcel
rate.

The whole question of subsidiary rates is dismissed by Bastable with the
following:--

"One of the principal distinctions now turns on the character of the
articles transmitted. Circulars and postcards would not bear the same
charge as ordinary letters. The transmission of newspapers gives a yet
smaller fund of utility on which to levy a tax, and is affected by the
competition of carrying agencies. The result is seen in the lower
halfpenny rate."--C. F. Bastable, _Public Finance_, London, 1903, p.
208.

[641] In England two-fifths of the total number of postal packets pass
at a halfpenny.

[642] The concession of specially low rates for these classes of packets
has given rise to a noteworthy general line of division between postal
packets. All packets passing at privileged rates must obviously be
subject to examination and check by the Post Office in order to ensure
that the privilege is not abused, a necessity which leads immediately to
the principle of the "open" post, as contrasted with the "closed" post,
the ordinary sealed letter packet. The difference in charge is not,
however, based on the consideration that the packets are open to
inspection. The effect is in the reverse direction. The view of
practical officers is that, other things