Underground Rivers - University of New Mexico

Chapter 5 -- The Crescent
The Extraction of Hidden Waters to the Surface by Persian mathematician
Al-Karaji (953-1029) distinguishes between phreatic, confined and perched
groundwater. Without reference to hydrostatic pressure, Al-Karaji properly
interpreted the physical basis for springs and artesian wells. He recognized
the hydrologic cycle.
The transformation of water into air in the hot regions and air into water in
the cold regions creates a constant cycle which guarantees the prosperity
of the lands.
Soviet postage stamp, 1993
Astronomer and geographer Al-Biruni (973-1048) was more explicit,
explaining water level in springs and artesian wells by the principle of water
finding its own level via interconnecting subterranean channels.
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Afghan postage stamp, 1973
The Islamic contribution to the study of underground rivers was thus twofold.
Unlike Christian appropriation of Hebrew scriptures, Qur'anic text lent itself to interpretation
consistent with what we now know as the hydrologic cycle
Islamic scholarship freed natural philosophy from theology. Speculation about underground
rivers hinged on logic and experience, not revelation. As we will see in the chapter to come,
such allowance would likewise come in the West, but more slowly and with more disputes.
At its climax, Islamic scholarship had surpassed Greek learning in many fields and created new
branches of mathematics and natural philosophy. But with the beginning of the second Christian
millennium, religious and political forces began to call us again westward.
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