150 NATURE OF CAPITAL AND INCOME  [Cmae. IX 
These two items constitute the transfer between the 
stock of books of the dealer and the stock of books of the 
customer. The remaining two items constitute a transfer 
between the stocks of cash of the two men; the dealer 
debits his “ cash” and the customer credits his. 
When therefore an article of wealth changes hands, 
it occasions an element of income to the seller and an 
element of outgo to the purchaser, and therefore no income 
at all to society. The effect of canceling these items — 
the credit item of the seller and the debit item of the pur- 
chaser — is to free the income account of that article from 
all entanglements with exchange, to wipe out all money 
income, and to leave exposed to view what we have called 
the natural income of the article. Thus, books yield their 
natural income, not when the book dealer sells them, but 
when the reader peruses them. The sale is a mere pre- 
paratory service, a credit item to the book dealer and a 
debit item to the buyer. The fact of bookselling adds 
nothing to the income of society, but the reading of the 
book does. Again, a forest of trees yields no natural 
income, until the trees are felled and pass into then ext 
stage of logs. The owner of the forest may, to be sure, 
“realize” on the forest long before it is ready to be cut, 
by simply selling it to another; and to him the forest has 
then yielded income; but, as the purchaser has suffered an 
equal outgo, the forest has as yet yielded nothing to society. 
The principle that an article of capital yields, to society, 
no income except its natural income, is not altered when 
its ownership is divided nor when the part rights are 
bought and sold. Adam Smith regarded a rented house 
as bearing income in the form of rent, but a house occu- 
pied by the owner as bearing no income at all. The truth 
is nearly the reverse. Both houses yield income, and both 
incomes are of the same kind, viz. shelter. The rent of the 
rented house is, for society, not income at all. It is income 
to the landlord but outgo to the tenant, — outgo which he