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De'nde campi apparcntis fcmidiamctcr cft '^-:;r. 

 circiter quadruplo maior quam in tubis \fitatis ; at 

 cft q—^^^~ , \ndc apertura. fccundae lcntis B hi- 

 mi debet. 



55. Circa numcrum ;/ cuiJcns eff , qno mir- 

 ior is accipintur, co minorcm prcxlirc longitudinem, 

 tum autcm fimul campus apparcns imminuitur. 

 Cum cniin per formuhis primum inuentas fit 

 Cp~sr=rTti), hic autem pofucrimus q~- *r,^^n ? vt 

 fit «ii:'^7ipT^ patct au(fto numero hoc ;/, etiam q 

 augcri , idcoque campum minui iu rationc numc- 

 ri 4 — (/. Pofito autcm «=i, fit q — ;~z^, ct 

 CPzr^^ oj ; tubus \cro aftronomicus \ulgaris pro 



cadem mukipHcationc pracbct (p— .tt^:;^^ oj , \nde 

 hoc cafu noftcr tubiis quadruplo ampliorem campum 

 dctcgit , fed ob «zi i, phis quam duplo lit longior. 

 Si crgo campus non 4. fcd 3! partibus amphor effe 

 debcat , llimi oportct n — '~'\ fin autcm 3; parti- 

 bus , fit fi — ~?^ , \nde patct admodum cxigua 



campi 



