om, and _tenens_, holding) consists in
holding off from the enjoyment of something which we have produced, or
might produce with the same labour. #To save# is to keep something whole
or untouched for future use; we save it as long as we do not consume it.
If I have a stock of flour and eat it up, there is an end of the flour,
and I cannot be said to save that. But if, while eating the flour, I am
engaged in making a plough or a cart, or any other durable thing which
will help me in production, I have turned one form of capital into
another form. I might have eaten the flour in idleness, in which case it
would not have been capital. But, while eating it, I worked for a future
purpose. In so doing I am said to #invest capital#, which means #to turn
circulating into fixed capital, or less durable into more durable
capital#. Capital, accordingly, is invested for longer or shorter
periods according to the durability of the form in which it is invested
(Latin, _in_, on, and _vestire_, to clothe). A good plough will perhaps
last twenty years; all through that time the owner should be getting
back by its use the benefit of the labour and capital spent in making
it. When it is worn out, he ought to have all the capital it cost paid
back, with some increase or interest. Capital invested in railway wagons
should pay itself back during the ten years that the wagons last on an
average.

The capital invested in any work may always be said to consist of wages
or what is bought with wages. Thus the capital invested in railways
really consisted of the food, clothes, and other commodities consumed by
the labourers who made the railways. It is true that tools also were
needed as well as the iron rails, sleepers, bricks, and other materials
required for the work. But as these things had previously been made by
labour, we may consider that the capital really invested in them was the
wages of the labourers who had already made them. Thus, #when we go far
enough back, we always find that the capital invested consisted of the
maintenance of labourers#.

#36. Investment of Capital.# We have two things to consider with regard
to the investment of capital, #firstly, the quantity of the capital#,
#and secondly, the length of time for which it is invested#. The same
quantity of capital will keep more or less men at work, according as it
is invested for shorter or longer periods. A man in growing potatoes
only needs to wait for the result of his la