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Another conclusioun to prove the height of the pool artik fro the orisonte.

Tak eny sterre fix that never descendith under the orisonte in thilke regioun, and considre his heighist altitude and his lowist altitude fro the orisonte, and make a nombre of bothe these altitudes; tak than and abate half

that nombre, and take there the elevacioun of the pool artik in that same regioun.