Wherever rent exists at all, differential rent appears at all times and is
 governed by the same laws, as agricultural differential rent. Wherever natural
 forces can be monopolised and guarantee a surplus-profit to the industrial
 capitalist using them, be it waterfalls, rich mines, waters teeming with fish,
 or a favourably located building site, there the person who by virtue of title
 to a portion of the globe has become the proprietor of these natural objects
 will wrest this surplus-profit from functioning capital in the form of rent.
 Adam Smith has set forth, as concerns land for building purposes, that the
 basis of its rent, like that of all non-agricultural land, is regulated by
 agricultural rent proper (Book I, Ch. XI, 2 and 3). This rent is distinguished,
 in the first place, by the preponderant influence exerted here by location upon
 differential rent (very significant, e.g., in vineyards and building sites in
 large cities); secondly, by the palpable and complete passiveness of the owner,
 whose sole activity consists (especially in mines) in exploiting the progress
 of social development, toward which he contributes nothing and for which he
 risks nothing, unlike the industrial capitalist; and finally by the prevalence
 of monopoly prices in many cases, particularly through the most shameless
 exploitation of poverty (for poverty is more lucrative for house-rent than the
 mines of Potosi ever were for Spain [38]), and the monstrous power wielded by landed
 property, when united hand in hand with industrial capital, enables it to be
 used against labourers engaged in their wage struggle as a means of practically
 expelling them from the earth as a dwelling-place.[39] One part of society thus exacts
 tribute from another for the permission to inhabit the earth, as landed
 property in general assigns the landlord the privilege of exploiting the
 terrestrial body, the bowels of the earth, the air, and thereby the maintenance
 and development of life. Not only the population increase and with it the
 growing demand for shelter, but also the development of fixed capital, which is
 either incorporated in land, or takes root in it and is based upon it, such as
 all industrial buildings, railways, warehouses, factory buildings, docks, etc.,
 necessarily increase the building rent. A confusion of house-rent, in so far as
 it constitutes interest and amortisation on capital invested in a house, and
 rent for the mere land, is not possible in this case, even with all the
 goodwill of a person like Carey, particularly when landlord and building
 speculator are different persons, as is true in England. Two elements should be
 considered here: on the one hand, the exploitation of the earth for the purpose
 of reproduction or extraction; on the other hand, the space required as an
 element of all production and all human activity. And property in land demands
 its tribute in both senses. The demand for building sites raises the value of
 land as space and foundation, while thereby the demand for elements of the
 terrestrial body serving as building material grows simultaneously. [40]