Here it circles around the Ile St. Louis, cutting it apart from the Ile de la Cité, and rushing up against the northern bank, periodically throws up a mass of gravelly sand, just in the precise spot where, in mediæval times, was an open market-place. Here the inhabitants of the city met the country dealers, who landed produce from their boats, traded, purchased, and sold, and departed whence they came, into the regions of the upper Seine or the Marne, or downward to the lower river cities of Meulan, Mantes, and Vernon. At this time Paris began rapidly to grow on each side of the stream, and became the great market or trading-place where the swains who lived up-river mingled with the hewers of wood from the forests of La Brie and the reapers of corn from the sunny plains of La Beauce. These country folk, it would appear, preferred the northern part of Paris to the southern--it was less ceremonious, less ecclesiastical. If they approached the city from rearward of the Université, by the Orleans highroad, they paid exorbitant toll to the Abbot of St. Germain des Prés. Here they paid considerably less to the Prévôt of Paris. And thus from very early times the distinction was made, and grew with advancing years, between the town, or La Ville, which distinguished it from the Cité and the Université. This sandy river-bank gradually evolved itself into the Quai and Place de la Grève,--its etymology will not be difficult to trace,--and endured in the full liberty of its olden functions as late as the day of Louis XV. Here might have been seen great stacks of firewood, charcoal, corn, wine, hay, and straw. [Illustration: THE ODÉON IN 1818] Aside from its artistic and economic value, the Seine plays no great part in the story of Paris. It does not divide what is glorious from what is sordid, as does "London's river." When one crosses any one of its numerous bridges, one does not exchange thriftiness and sublimity for the commonplace. Les Invalides, L'Institut, the Luxembourg, the Panthéon, the Odéon, the Université,--whose buildings cluster around the ancient Sorbonne,--the Hôtel de Cluny, and the churches of St. Sulpice, St. Etienne du Mont, and St. Severin, and, last but not least, the Chamber of Deputies, all are on the south side of Paris, and do not shrink greatly in artistic or historical importance from Notre Dame, the Louvre, the Tour St. Jacques, the Place de la Bastille, the Palais Royal, or the Théâtre-Français. The greatest function of the Seine, when one tries to focus the memory on its past, is to recall to us that old Paris was a trinity. Born of the river itself rose the Cité, the home of the Church and state, scarce finding room for her palaces and churches, while close to her side, on the south bank, the Université spread herself out, and on the right bank the Ville hummed with trade and became the home of the great municipal institutions.