THE NATURE OF AGENCY. 509 understanding of the parties? If we find present these elements of custom, we may ask further, With reference to what custom did the parties deal? which is the same thing as to ask. What custom did they incorporate into their understanding? Obviously, the last question is precisely identical with the first. Questions of the understanding of two parties are typical ques- tions of fact, and are usually in our jurisprudence so treated, that is to say, they are usually left to the jury for determination. When, however, these elements of custom enter, they have been frequently arrogated by the court to its own province, and then these questions are called questions of law. The process by which this was effected is plainly visible. In the times of Mansfield and Holt, when the great expansion from the old feudal narrowness into our more modern conditions first began in Anglo-Saxon law, with new and difficult cases of custom, the court not infrequently called in the aid of men familiar with such transactions. Their statements were accepted by the court; they were mentioned in judicial opinions, or included in reporters' statements of fact, and, thereby passing into the books, became precedents, and are now familiar learning.^ In all such cases, however, the imperative obligation of following the intention of the parties still obtains, and he who would do justice must recognize that what is called a rule of law is in such cases but a canon of construction. With this in mind, I propose to examine certain simple and typical cases which present the separation of which I have spoken, and which are not infrequently the subject of much confusion. I . Suppose that I convey to A certain property which I direct him thereafter to hold to certain nses prescribed by me. Here we find the separation of the plan from the execution of it. I have conceived certain purposes which, for various reasons, A undertakes to execute. The effective accomplishment of them is dependent upon the communication estabHshed between us. 1 For example, the English court frequently consulted with the merchants of Lon- don with reference to the custom of merchants, then first obtaining judicial recogni- tion. In Buller v. Crips, 6 Mod. 29 (1704), which was the famous case in which Chief Justice Holt undertook to decide that promissory notes were not negotiable instru- ments, the reporter states that " at another day, Holt, C. J., declared that he desired to speak with two of the most famous merchants in London, to be informed of the mighty ill consequences that it was pretended would ensue by obstructing this course." In that case, indeed, the Chief Justice declined to follow their opinion and was in conse- quence overruled by St. 3 & 4 Anne, c. 9, §§ 1-3 (1704). 67
