However, the practical needs of chroniclism and of learning make themselves felt here also. Just as in metrical treatises the internal rhythm of a poem is resolved into external rhythm and divided into syllables and feet, into long and short vowels, tonic and rhythmic accents, into strophes and series of strophes, and so on, so the internal time of historical thought (that time which is thought itself) is derived from chroniclism converted into external time, or temporal series, of which the elements are spatially separated from one another. Scheme and facts are no longer one, but two, and the facts are disposed according to the scheme, and divided according to the scheme into major and minor cycles (for example, according to hours, days, months, years, centuries, and millenniums, where the calculation is based upon the rotations and revolutions of the earth upon itself and round the sun). Such is _chronology_, by means of which we know that the histories of Sparta, Athens, and Rome filled the thousand years preceding Christ, that of the Lombards, the Visigoths, and the Franks the first millennium after Christ, and that we are still in the second millennium. This mode of chronology can be pursued by means of particularizing incidents thus: that the Empire of the West ended in A.D. 476 (although it did not really end then or had already ended previously); that Charlemagne the Frank was crowned Emperor at Rome by Pope Leo III in the year 800; that America was discovered in 1492, and that the Thirty Years War ended in 1648. It is of the greatest use to us to know these things, or (since we really _know_ nothing in this way) to acquire the capacity of so checking references to facts that we are able to find them easily and promptly when occasion arises. Certainly no one thinks of speaking ill of chronologies and chronographies and tables and synoptic views of history, although in using them we run the risk (and in what thing done by man does he not run a risk?) of seeing worthy folk impressed with the belief that the number produces the event, as the hand of the clock, when it touches the sign of the hour, makes the clock strike; or (as an old professor of mine used to say) that the curtain fell upon the acting of ancient history in 476, to rise again immediately afterward on the beginning of the Middle Ages.