CHRONOLOGY—CULTURE-GAPS. 53 
be added the unknown equivalent of the time consumed in the cutting-down that 
began towards the end of the copper culture and deepened the valley 20 feet. 
While we have no determination of the rate of this deepening of the valley, we may 
assume that, being dependent on the compensatory orographic process of load- 
shifting, it was neither spasmodic nor unduly rapid. Even if we should assume 
what would seem an improbable rate of 2 feet per century, this 20 feet of cutting- 
down would require 10 centuries, the equivalent of 20 feet of culture-strata. Even 
this, added to the 30 feet equivalent of the aggrading, would insert the time-equiva- 
lent of 50 feet of culture-strata between the beginning of the cutting-down and 
the founding of Anau. A slower rate of cutting would lengthen the gap and time. 
Of the 30 feet required as the minimum culture equivalent of the aggrading, 
14 feet belong before the iron culture, and represent that portion of the gap between 
copper and iron. Also, for the cutting-down of at least 20 feet, we have only 
the last 8 feet of copper culture-strata. From these geological considerations it 
is clear that the gap between the copper and iron is very considerably greater 
than the 14 feet determined by the aggrading. 
Having explained the available geological factors, let us see what the copper 
culture itself offers. While the whole of this culture was characterized by an 
abundant use of copper for ornaments, domestic implements, and weapons of the 
earliest forms, not only was tin not used for hardening the metal, but, with the 
single exception of a ring, it did not occur in any of our finds until towards the end. 
Therefore these people lacked not only knowledge of full tin-bronze (9 to 10 per 
cent tin), but they were not even in the transition stage in which smaller percent- 
ages of tin were used intentionally in cutting-implements. 
Now a large proportion of our copper finds in the South Kurgan, including 
cutting-implements, daggers, etc., were found in intimate association with objects 
belonging to civilizations in the Chaldean sphere of influence, especially the asso- 
ciated figurines of naked Ishtar and of the cow or bull. We do not know how 
early full tin-bronze or even the lower alloy was known in Babylonia, but this 
knowledge could not fail* to be nearly contemporaneous in Babylonia and Egypt. 
Montelius, after a careful survey of the whole field of existing knowledge of the 
subject, decides that the use of full tin-bronze (9 to 10 per cent of tin) came into 
Egypt in the XI or XII dynasty, and that small amounts of tin are found in objects 
of the earlier dynasties. The probable Central-Asiatic origin of the lapis lazuli 
used in Egypt at least as early as the XII dynasty is, to the extent of that proba- 
bility, evidence of commercial relations between Egypt and Babylonia. ‘The 
most conservative chronology—that of the Berlin schools—places the beginning 
of the XII dynasty at 2000 to 2200 B. c., and we are warranted in accepting 
this as about the date of the introduction of full tin-bronze in Mesopotamia. In 
view of these considerations I have felt justified in placing the end of the copper 
culture of the South Kurgan at 2200 B. c., as the latest probable date, and have 
left in the column a gap equal in feet to the requirements of this determination. 

*According to Montelius, 1900, no tin has been found in any of the older objects of copper from Tello 
and other Babylonian localities. It has been found in objects from graves at Ur and Erech, which range 
from the second half of the III to the end of the II millennium. 
