不等臂天平的出现，其前提条件是制造者对杠杆原理的掌握。
The essential prerequisite for using lever scale is that its maker knew the principle well.
浮力天平的测量是利用阿基米德定理，计算出配重物体受到的浮力，再通过杠杆平衡的原理得出配重物体浮力的变化即被测量物体的重量。
Based on Archimedes theorem and lever balance principle, we can calculate the buoyancy's variety of the balance objects. This variable just equals to the weight of the measured object.
195一切天平的一切垂直杠杆，均凭借其结构来证实表面上的平衡中的谬误。
195the false apparent parallelism of all perpendicular arms of all balances, proved true by construction.
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