Porta, Giambattista della, approximately 1535-1615, Gaywood, Richard, active 1650-1680, engraver, Young, Thomas, active 1658, publisher, Speed, Samuel, -1681, publisher · London : Printed for Thomas Young and Samuel Speed and are to be sold at the three pigeons, and at the angel in St. Paul's Church-yard · leaf 393
The fame is to be faid of the beam M H and N G, and this Glafs is contrary to a Sphaeral Glafs : From divers points of the circumference, the rays are reflected upon different parts of the diameter, and all the diameters are from the Centre: but in this the refie&ed beams unite, not in one point,… … Chap. XIX. Fire it kindled more forcible by refrattion. I Have fpokenof Burning-glafTes by reflection : Now I fhall fpeak of thofe which burn by refraction; for thefc kindle fire more violently , I fhall fhew my reafon in the Optick?. Wherefore By 4 Cylindre of Cryfttl to kindle fire. We may do it…
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