onopoly of a business, it is evident that to
charge the price which would bring in the largest profit would often be
simply equivalent to laying a tax on the commodity. In this case, the
price charged should only be such as would produce a rate of interest
which would satisfy private individuals or joint-stock companies,
supposing there were no monopoly. The rate of interest should be
reckoned in relation to the actual market value of the property used,
not in relation to what it may have originally cost the State. When the
State makes a bad investment the loss should be written off once for all
as soon as it is discovered. If, for instance, a State has bought
telegraph apparatus for far more than it is worth, there can be no
reason why the senders of telegrams, and not the whole body of
taxpayers, should pay for the mistake."--Edwin Cannan, _Elementary
Political Economy_, London, 1903, pp. 130-1.

The cost which ought in strictness to be taken is the cost of the most
economical private commercial undertaking which would provide an equal
service if the monopoly of the Post Office were withdrawn:--

"I do not regard the greater part of the Post Office revenue as a tax at
all. If all of it were earned by doing for the public on a large scale
work that no private company could do as cheaply, because it would have
to do it on a small scale, then I should say that none of the Post
Office revenue was a tax. That part, however, of its revenue which it
gets by prohibiting others from performing services for the public is a
tax."--Alfred Marshall, _The Times_, 6th April 1891.

[745] The terms "Mixed Taxes" and "Quasi-Taxes" have been applied to
charges of this character. "Mixed Taxes, or Quasi-Taxes, naturally arise
when a governing body makes demands for payments, and gives something in
return, but without any pretence of equivalence between individual
payments and individual returns."--R. Jones, _The Nature and First
Principle of Taxation_, London, 1914, p. 7.

[746] E.g. "Many definitions of the word 'tax' have been proposed, but I
know of none which would include just so much of the Post Office revenue
as happens to be in excess of the amount expended in the year and no
more.

"I believe that the desire to reckon this amount and no more as a tax,
arises from a somewhat dim impression that it is the sum which the State
exacts in excess of what a private company, without any legal or natural
monopoly, would have to be sat