Sec. 8] INCOME SUMMATION 147 
ever, on the part of the stock of cotton, an element of outgo 
or expense. 
As has already been intimated, there may be, and usually 
are, more articles than one in either or both of the two 
interacting capitals. Plowing, or the transformation of 
land into a furrowed form, is performed by a plow, a horse, 
and a man. The plowing is a cost debited to the land on 
the one hand, and at the same time a service credited to 
the group of capital consisting of the plow, horse, and man 
on the other. We are not here concerned with the problem 
of how much should be placed to the credit of each co- 
operating agent, but merely with the fact that the sum 
total of the three is equal to the debit for the land. 
The principle is not altered if one or more of the trans- 
forming agents perishes and another comes for the first time 
into existence in the transformation. Bread-baking is a 
transformation debited to the bread and credited to the 
cook, the range, the flour, and the fuel, of which the last 
two perish as soon as they perform their services. Agents 
which disappear in the transformation but reappear, in 
whole or in part, in the product are called “raw materials.” 
The production of cloth from yarn is a transformation ef- 
fected by means, not only of the loom, but also of a number 
of other agents, and among them the yarn itself. The cost 
of weaving includes as cost the consumption of raw material, 
yarn, and this consumption of yarn, on the part of the 
yarn itself, is not cost or disservice, but service. It is 
the event for which the yarn had existed. When cloth 
is turned into clothes this transformation is a service to 
be credited to the cloth, and a disservice to be debited to the 
clothes. All raw materials yield services as they are con- 
verted into finished products. Their conversion is, however, 
always outgo on the part of those products. 
In this way, when an article passes through various stages 
of production, it is often an arbitrary matter whether we 
designate those stages by different names or not. A “sap-