What did scientists contribute?

Look at the expectation: it asks what scientists contributed. Ask whether a contribution is a new idea, a new instrument or a refinement of one that existed, and how a source lets you tell them apart.

Look at the balance of wisdom as a measuring instrument. Robert Hall describes a long beam, a sensitive indicator tongue and five pans used in different arrangements, including one in which the object is immersed in a known liquid ². He specifies a beam four cubits long, approximately two metres in his conversion, and an indicator around half a metre long ². He reports al-Khazini's claimed sensitivity of one part in 60,000 to one in 100,000 for a load around 4.5 kilograms, the range depending on a historical unit's value ². Sensitivity also depends on suspension, careful construction and the long tongue, not merely the number of pans ².

The records preserve no sentence in which al-Khazini or al-Biruni says why the instrument was made. For al-Khazini they show a frame stated in his own book: its preface brings knowledge, action and justice together, placing reliable measurement within a wider conception of fairness ³. Hall reads the name of the balance in both technical and ethical senses: sound discrimination of genuine and adulterated materials, alongside a well-founded and carefully constructed instrument ⁴. For al-Biruni's vessel they preserve no such statement.

Figures printed beside a device are easy to give to the wrong man. The transmitted illustration names Abu Rayhan's conical instrument ⁵. After the description, page 55 of Khanikoff's publication discusses "our author" experimenting with it, and in this publication that means al-Khazini ⁶. His repeated trials and the following table must not automatically become al-Biruni's own observations ⁶.

Ansari says the Beirut manuscript of al-Biruni's treatise and Cheikho's communication were unavailable to him, so this part of his preliminary study relies on Wiedemann ⁷. For the balance, the illustrated witness is Penn's manuscript LJS386, which Penn describes as an undated copy probably made between the later thirteenth and earlier fourteenth centuries, expressed as 1250?–1350? ⁸. The date 515/1121–1122 belongs to the treatise, not to the later manuscript pictured ^4 8. Ask how many hands stand between each figure and the man it is credited to.

Hall classes al-Khazini's work as an improvement, and credits al-Asfizari with the earlier movable pans ⁹. Does a refinement of an inherited instrument count as the kind of contribution your curriculum asks you to describe, and what is the strongest objection to your answer?

• The balance of wisdom: the beam, the pans and the claim about sensitivity, with Hall's account of who added what.
• Al-Biruni's displacement vessel: the conical vessel, and why the drops in its tube matter.
• Al-Khazini: the author of the treatise and the questions about his identity.
• Al-Biruni: the scholar to whom the vessel is attributed.