Points C and C' begin moving simultaneously to the right, starting at A and A' respectively with the same initial velocity; C' moves with uniform velocity and C with a velocity which is equal to the distance CB. Napier defined A'C' (= y) as the logarithm of BC (= x), that is
Points C at C 'simulan ang paglipat ng sabay-sabay sa kanan, simula sa isang at isang' ayon sa parehong unang katulinan; C 'inililipat sa unipormeng bilis at C na may kabilisan na kung saan ay pantay na ang layo CB. Napier tinukoy A 'C' (= y) bilang ng logarithm ng BC (= x), na