Having thus obtained a knowledge of the principles of the science, facility in manipulation, and reliance on his own powers of observation, the student should begin quantitative analytical work, in which he learns by degrees what scientific accuracy means, and how exact results are to be obtained by careful work. Constant personal supervision of the student is absolutely requisite, as everything depends on the care with which the various operations are carried on, working from recipes without superintendence being really valueless. One main object of this course is so to teach the pupil as to give him reliance on his own power of exact work; to inculcate habits of neatness and order; to make him aware of sources of error, and to teach him either to estimate their amount, or how, if possible, to obviate them. On this firm foundation of a competent theoretical knowledge of inorganic and organic chemistry, and of a thorough practical acquaintance with analysis, can alone the proper and higher education of the chemist, whether for purely scientific or for technical purposes, be based. It was upon this view Roscoe consistently acted. He steadily set his face against any practising of rough-and-ready works-methods until the student had learnt to appreciate the exacter processes. It is only when he has gained the capacity for judging as to the particular applicability of a method that he should be permitted to compromise between efficiency and speed. When confidence is based upon knowledge and practice, the special circumstances of his position and his sense of responsibility, when engaged in technical work, will enable him to determine rightly when such compromise is justifiable. As regards instruction in applied chemistry, Roscoe always held that the application can only be properly learnt in the factory or works, just as a trade cannot be taught in a school—unless, indeed, the school becomes a shop. But there is no reason why the scientific principles and details of the various industrial processes should not be brought to the knowledge of the pupil who is intended afterwards to conduct such processes. Provided a sound scientific basis is secured, such instruction, given by a teacher who has had practical as well as theoretical experience, is of great value to the technical student.