Karaji has introduced and explained the leveling instruments which were used at that time, in his book Inb?t? al-miah al-khafiyyat (Exploration for hidden water). Added to the four studied leveling instruments, Karaji introduces two more; “scaled vertical level” and “scaled telescopic level” which he mentions as his own inventions. In this paper after presenting these first four, the two levels have been studied emphasizing on Karaji’s calibration method and some examples of their application.
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