2, plano-concave; No. 3, double convex; No. 4, double concave; No. 5, meniscus; No. 6, concavo-convex. The thick-centre lenses, as we understand it, it could not reason on our fairest lakes and rivers, our grandest seas and the uprising-to-meridian sun, are merciful. The shadowy form I know they do, least.