The next thing to be considered is, whether there may not be some act of consent besides silence. For without some visible act, silence is not of itself sufficient to warrant a probable conjecture of intention. But if certain acts are done which can be accounted for upon no other grounds than those of consent, they are supposed to ratify a treaty. Thus if the convention of Luctatius had contained many clauses, some of them relinquishing certain rights, and those clauses had been always duly observed by the Romans, such observance would be justly taken for a ratification of the treaty. CHAPTER XVI. THE INTERPRETATION OF TREATIES. The external obligation of promises--Words where other conjectures are wanting to be taken in their popular meaning--Terms of art to be interpreted according to the acceptation of the learned in each art, trade, and science--Conjectures requisite to explain ambiguous or seemingly contradictory terms--Interpretation of treaties from the subject-matter--From consequences, from circumstances and connection--Conjectures taken from motives--The more strict or more extensive interpretation--Treaties favourable, odious, mixed or indifferent--The good faith of kings and nations in treaties of equal validity with law--Rules of interpretation formed from the above named distinctions--Whether the word allies, in a treaty, is limited to those, who were such at the time of making it, or applies to all who are, or hereafter may become such--Interpretation of the prohibition of one party's making war without the consent or injunction of the other--Of the freedom granted to Carthage--Distinction between personal and real treaties--A treaty made with a king continues even during his expulsion by an usurper, such a treaty extends not to an invader--What kind of promises ought to have the preference--The extent of obvious conjectures--The performance of a commission by doing something equivalent--Interpretation restricted more closely than the bare signification of the words implies--From an original defect of intention--From failure of the sole motive--From a defect in the subject--Observations on the last named conjectures--Emergencies repugnant to the original intention, by rendering it unlawful or burdensome--Conjectures taken from a comparison of one part of the writings with another--Rules to be observed--In dubious cases, writings not absolutely requisite to the validity of a contract--Contracts of Sovereigns not to be interpreted by the Roman law--Whether the words of the person accepting or offering the engagement ought to be most regarded--This explained by a distinction.