The commerce of literature has been doubled in twenty years. But it would be scarcely too much to assert that the influence of the press, in forming public opinion, and causing it to operate upon legislation, has doubled almost every other employment. To that public opinion, chiefly so formed, we owe the successive removals of restrictions upon trade, which have carried forward our exports from thirty-six millions sterling in 1831 to ninety millions in 1853. To that public opinion we owe the abolition of prohibitive duties upon foreign produce, which has given us a far wider range of beneficial consumption. To that public opinion we owe the repeal of the oppressive excise duties upon salt, leather, candles, glass, bricks--which duties impeded production even more effectually than the extortions and tyrannies of the middle ages. Strange it is, that the power of the press, which has done so much for the removal of other fiscal impediments to industry, should have been able to effect so little for itself;--that the tax upon paper should still interfere with the commerce of literature, when general education has no longer to encounter any misgivings in the minds of those who govern an earnest and patriotic people. The difficulty of procuring the material of paper has become a serious impediment to the cheap diffusion of knowledge; and the paper-tax works in the same evil direction. There have been innumerable obstacles to the extension of knowledge since the days when books were written on the papyrus--obstacles equally raised up by despotic blindness and popular ignorance. But it is not fitting that either of such causes should still be in action in the days of the printing-machine. CHAPTER XXII. Power of skill--Cheap production--Population and production--Partial and temporary evils--Intelligent labour--Division of labour--General knowledge--The Lowell Offering--Union of forces.