1To Benjamin Franklin from Christian Emanuel Frolich: Résumé, 7 April 1781 (Franklin Papers)
ALS : American Philosophical Society <Görlitz, Silesia, April 7, 1781, in German: We would be...
2To Benjamin Franklin from Ingenhousz, 7 April 1781 (Franklin Papers)
ALS : American Philosophical Society I did send you in Decembre last the issue of the experiment...