2. The obligations of the second class, as they were contracted by the delivery of a thing, are marked by the civilians with the epithet of real. A grateful return is due to the author of a benefit; and whoever is intrusted with the property of another has bound himself to the sacred duty of restitution. In the case of a friendly loan, the merit of generosity is on the side of the lender only; in a deposit, on the side of the receiver; but in a pledge, and the rest of the selfish commerce of ordinary life, the benefit is compensated by an equivalent, and the obligation to restore is variously modified by the nature of the transaction. The Latin language very happily expresses the fundamental difference between the _commodatum_ and the _mutuum_, which our poverty is reduced to confound under the vague and common appellation of a loan. In the former, the borrower was obliged to restore the same individual thing with which he had been accommodated for the temporary supply of his wants; in the latter it was destined for his use and consumption, and he discharged this mutual engagement by substituting the same specific value according to a just estimation of number, of weight, and of measure. In the contract of sale, the absolute dominion is transferred to the purchaser, and he repays the benefit with an adequate sum of gold or silver, the price and universal standard of all earthly possessions. The obligation of another contract, that of location, is of a more complicated kind. Lands or houses, labor or talents, may be hired for a definite term; at the expiration of the time the thing itself must be restored to the owner, with the additional reward for the beneficial occupation and employment. In these lucrative contracts, to which may be added those of partnership and commissions, the civilians sometimes imagine the delivery of the object, and sometimes presume the consent of the parties. The substantial pledge has been refined into the invisible rights of a mortgage or _hypotheca_; and the agreement of sale, for a certain price, imputes from that moment the chances of gain or loss to the account of the purchaser. It may be fairly supposed that every man will obey the dictates of his interest; and if he accepts the benefit, he is obliged to sustain the expense of the transaction. In this boundless subject, the historian will observe the _location_ of land and money, the rent of the one and the interest of the other, as they materially affect the prosperity of agriculture and commerce.