Cas. 2. Transeat jam corpus successive per spatia plura parallelis planis terminata, AabB , BbcC &c. & agitetur vi quæ sit in singulis separatim uniformis, at in diversis diversa; & per jam demonstrata, sinus incidentiæ in planum primum Aa erit ad sinum emergentiæ ex plano secundo Bb , in data ratione; & hic sinus, qui est sinus incidentiæ in planum secundum Bb , erit ad Page 229 sinum emergentiæ ex plano tertio Cc , in data ratione; & hic sinus ad sinum emergentiæ ex plano quarto Dd , in data ratione; & sic in infinitum: & ex æquo sinus