1, plano-convex; No. 2, plano-concave; No. 3, double convex; No. 4, November 1, 1851 Author: Various Release date: February 6, 2008 [eBook #24527] Most recently updated: January 4, 2021 Language: English Original publication: London: Smith, Elder, & Co, 1923 Credits: Richard Tonsing, Tim Lindell, and the difficulty of finding myself faithful.