In horum defedu poflfunt adhibcri lapides arenacei intus circa centrum pariimexcavati, ut ita annularem figuram cxhibeant. Debent autem lapidcs feJigi, quiprsdura cratrmfculaarena conftant. 7. Scutellarum perfedio examinari poteft fidicula valde tcnui, aut longiori Quomo-pilo pcrfcutellae…
Optics, Geometrical · Optical instruments
Internet Archive · Getty Research Institute · Public Domain Mark 1.0. Free to use for anything.