Nor must we forget to hint at the discoveries which have given new effect to surgical skill--the discovery of anaesthetics, the perfection of artificial limbs, the repair of the body, and the valuable method of lithotrity; while even the match need not be disdained as one of the chief inventions of the century. Paper, too, and engraving, and printing (with all its complications of stereotyping, electrotyping, and heliotyping), photography (with its constant improvements), can only be mentioned to open the mind to a wide vista of marvellous triumphs. We have but to glance along the stalls of a modern book-store, to appreciate that the arts of printing and engraving have made a more rapid progress during the past hundred years than during all the previous centuries since the invention of type; while it may fairly be said that the United States can at last boast that not only is her literature worthy to be compared with that of England, but that it is as well printed, illustrated, and bound, and is presented on home-made paper as elegant and as durable, as are the choicest publications of London and Paris. XIX. POLITICAL CHANGES. [Sidenote: Sources of Government.] President Woolsey has forcibly remarked that states and forms of government have had mainly two sources of origin. They have either "slowly built themselves up for ages, finding support in historical causes, and in past political habits"; or, they have been "the artificial results of political theory." England presents the most conspicuous modern example of the former class; while France, since the Revolution, may be regarded as the chief modern example of the latter. And as it was with England, our mother-country, so it has been, and is, with us. It is true that the organism of the United States was the immediate result of revolution, and is founded upon a constitution that is written and fixed, or only with great pains and difficulty modified. Yet, if we search further and deeper for the materials of which our national fabric has been constructed, we shall easily recognize that our freedom, like that of England, has really "broadened slowly down from precedent to precedent." [Sidenote: Gradual Growth of the American System.] The growth towards American independence did not begin, the seeds of it were not sown, either at Bunker's Hill or at Philadelphia. Indeed the growth had then reached the period of fruitfulness. The progression towards an independent nation, and a free nation, began at Plymouth and at Jamestown. The Constitution only made articulate the spirit which had been growing for more than a century, and it still left an unwritten law set up by custom, habit, and characteristics most aptly nourished to the ends reached in 1776, 1787, and 1789. While our written constitution was made, we still retained the common law of England as the basis of our own, and, like England, proceeded gradually to build upon this broad foundation the superstructure of statute.