There is a great difficulty in the way of a writer who attempts to sketch a living Constitution—a Constitution that is in actual work and power. The difficulty is that the object is in constant change. An historical writer does not feel this difficulty: he deals only with the past; he can say definitely, the Constitution worked in such and such a manner in the year at which he begins, and in a manner in such and such respects different in the year at which he ends; he begins with a definite point of time and ends with one also.