All dates are based on Egyptian chronology. Even approximate dates cannot yet be given for the Early Minoan or Early Helladic periods. The Early and Middle Helladic periods do not correspond exactly with the Early and Middle Minoan periods respectively. Some scholars synchronize Middle Helladic II with Middle Minoan III. Only the three late styles coincide in Crete and Greece.
The characteristics of Cretan art have been thoroughly dealt with by G. A. S. Snijder, Kretische Kunst, 1936.
The classifications of Early, Middle and Late Minoan and Helladic styles do not do full justice to the real development of the styles in Crete and on the Greek mainland. I have therefore tried to characterize and limit the main stages in the evolution of styles by other denominations. Thus the different lines of development on the mainland and in Crete become apparent. By "Greco-Helladic" style I mean that period which represents the final stage of development of Helladic civilization, the first "Greek style" prior to the Dorian migration. Figs. 455, 459, 463, 470 and 512 illustrate the fact that from that period on there was only a short evolution to the stage of art which we term Greek art proper. At any rate there is evidence that an important and budding culture was destroyed by the Dorian invasion.
I borrowed the terms Late Helladic IV and V from W. A. Heurtley ( "The Quarterly of the Department of Antiquities in Palestine" Vol. 1936, p. 90, footnote I). The chronology of the culture of the Cyclades, which mostly coincides with the Early Helladic period, is still a matter of dispute; cf. especially the investigations of N. Aberg, Bronzezeitliche und früheisenzeitliche Chronologie Vol. IV ( 1933). In this volume, as in the third ( 1932), the Cretan and Mycenaean chronologies are thoroughly investigated.
As to the use of iron, see A. W. Persson, "Eisen und Eisenbereitung in älterer Zeit" (Lund Ars berättelse 1933/34, VI). A small piece of iron was found in a tomb near Cnossus dating already from the Middle Minoan period (about 2000 B. C.). Iron is more frequently found in the dome and chambertombs in the shape of rings (cf. Fig. 177) which points to the fact that is was probably considered as valuable as gold; but it was not till the Dorian migration that it was used for the manufacture of weapons and implements.