The key to the whole system is thus the unit course of three months' instruction in a single subject. The method of such a course is conveyed by the technical terms lecture, syllabus, exercises, class. The lectures are addressed to audiences as miscellaneous as the congregation of a church, or the people in a street car; and it is the duty of the teacher to attract such miscellaneous audiences, as well as to hold and instruct them. Those who do nothing more than simply attend the lectures will at least have gained the education of continuous interest; it is something to have one's attention kept upon the same subject for three months together. But it may be assumed that in every such audience there will be a nucleus of students, by which term we simply mean persons willing to do some work between one lecture and another. The lectures are delivered no oftener than once a week; for the idea is not that the lectures convey the actual instruction--great part of which is better obtained from books, but the office of the lecture is to throw into prominence the salient points of the study, and rouse the hearers to read, for themselves. The course of instruction is laid down in the syllabus--a document of perhaps thirty or forty pages, sold for a trifling sum; by referring for details to the pages of books this pamphlet can be made to serve as a text-book for the whole course, making the teacher independent in his order of exposition of any other text-book. The syllabus assists the general audience in following the lectures without the distraction of taking notes; and guides the reading and thinking of the students during the week. The syllabus contains a set of 'exercises' on each lecture. These exercises, unlike examination questions or 'quizzes,' are not tests of memory, but are intended to train the student to work for himself; they are thus to be done under the freest conditions--at home, with full leisure, and all possible access to books, notes or help from other persons. The written answers are sent to the lecturer for marginal comment, and returned by him at the 'class.' This class is a second meeting for students and others, at which no formal lecture is given, but there is free talk on points suggested to the teacher by the exercises he has received: the usual experience is that it is more interesting than the lecture. This weekly routine of lecture, syllabus-reading, exercise and class goes on for a period of twelve weeks. There is then an 'examination' in the work of the course held for students who desire to take it. Certificates are given by the university, but it is an important arrangement that these certificates are awarded _jointly_ on the result of the weekly exercises and the final examination.