 Sir David Brewster found that Wollaston's form worked best when the two lenses were hemispheres and the central space was filled up with a transparent cement having the same refractive index as the glass.He therefore used a sphere from a single piece of glass with a deep groove cut in it.In 1829, Henry Coddington brought the Wollaston–Brewster lens into general notice and further refined the design by modifying the shape of the groove, though Coddington laid no claim to being its inventor.