3. Now, I believe it to be wholly impossible to teach special application of Art principles to various trades in a single school. That special application can be only learned rightly by the experience of years in the particular work required. The power of each material, and the difficulties connected with its treatment are not so much to be taught as to be felt; it is only by repeated touch and continued trial beside the forge or the furnace, that the goldsmith can find out how to govern his gold, or the glass-worker his crystal; and it is only by watching and assisting the actual practice of a master in the business, that the apprentice can learn the efficient secrets of manipulation, or perceive the true limits of the involved conditions of design. It seems to me, therefore, that all idea of reference to definite businesses should be abandoned in such schools as that just established: we can have neither the materials, the conveniences, nor the empirical skill in the master, necessary to make such teaching useful. All specific Art-teaching must be given in schools established by each trade for itself: and when our operatives are a little more enlightened on these matters, there will be found, as I have already stated in my lectures on the political economy of Art,[59] absolute necessity for the establishment of guilds of trades in an active and practical form, for the purposes of ascertaining the principles of Art proper to their business, and instructing their apprentices in them, as well as making experiments on materials, and on newly-invented methods of procedure; besides many other functions which I cannot now enter into account of. All this for the present, and in a school such as this, I repeat, we cannot hope for: we shall obtain no satisfactory result, unless we give up such hope, and set ourselves to teaching the operative, however employed--be he farmer's laborer, or manufacturer's; be he mechanic, artificer, shopman, sailor, or plowman--teaching, I say, as far as we can, one and the same thing to all; namely, Sight.