SEQUENCE DATING. A sequence date (adopted in Ger many as Staffelzahl) is a dating by relation to things earlier and later in arbitrary units, not by years. All history is mainly con cerned with the order of events; the dates A.D. are of much less consequence than the connection of cause and effect. To know that the Armada preceded the Stuarts is essential; that it was 15 years earlier is a detail. In ages where no dated history exists our endeavour must be to put what we know into its true order.
The most obvious kind of evidence of sequence is in geology, when strata lie deposited one on the other, and similarly in human settlements when buildings or refuse heaps are superimposed. Such evidence is finally conclusive, where accidents do not occur. (See STRATIGRAPHY.) But changes do occur, and may upset the evidence. Strata may be deficient where contact is sought, or may have been separated by a sill of molten rock, or have suffered overthrust by compression, or even been altogether inverted. In strata of man's works burrowing animals or men may upset order and let objects shift far down, or throw them up ; dyed wool occurred in a prehistoric grave, but it had been carried down by a rat for lining its nest ; the Persians dug granaries 20 feet deep through many centuries of town levels.
Another kind of evidence of sequence is that from the style of objects. Suppose in a great mansion that the room in which each master had died was left with its furniture untouched. If we could thus compare the surroundings of each generation we should have little or no doubt as to the sequence of the rooms. The changes of fashion—Victorian, Regency, French Revolution, Georgian—would make it impossible to mistake the order, so as to put a Chippendale sofa between the '51 and '62 Exhibition periods. There is the ancient equivalent of such successive rooms in the funeral outfit for the dead. Each generation varied the forms of its objects—pottery, weapons, ornaments—and the con nection of the varieties can thus be traced. (See TYPOLOGY.)
Establishing a Dating.—If, then, we are able to put a large number of graves into their relative order, we need to be able to denote each part of the series. This may be done by dividing a series of, say, i,000 graves into so parts, of about 20 graves in each part. Thus we have a series of divisions that may be num bered consecutively, and so form a chain of periods, though not of equal periods of years ; they are periods of equivalent mortal ity or productivity. Yet such numbers of the periods, or sequence dates, constitute as true a history as if they specified the date in years. The stages of perceptible change are not so close together as single years; they may be most nearly generations, or centu ries, or even millennia in early ages of man. The method of numbering them in order gives the handle by which to use the history of prehistoric ages, as familiarly as we refer to the years or centuries of written history. An ancient dating by numbers is already familiar in the naming of the successive dynasties of Egypt from I to 3o ; a mode of reference which avoids the differ ences of opinion about the dates in years.