His treatises De mensura astrolabii and De utilitatibus astrolabii (to be found, on the authority of Salzburg MSS., in Pez, Thesaurus anecdotorum novissimus, iii.) being the first contributions of moment furnished by a European to this subject, Hermann was for a time considered the inventor of the astrolabe.
In the 9th Alcuin sends to Charles the Great for a copy of the earlier books (Epp. 103, Jaffe); and Dicuil gathers extracts from the pages of Pliny for his own Mensura orbis terrae (c. 825).
Two years later appeared his Recherches geographiques et critiques on the De Mensura Orbis Terrae of Dicuil.
He was the author of the De mensura orbis terrae, finished in 825, which contains the earliest clear notice of a European discovery of and settlement in Iceland and the most definite Western reference to the old freshwater canal between the Nile and the Red Sea, finally blocked up in 767.
Since that time, however, valuable maps have been published by an Oficina de mensura de tierras, by a seccion de geografia y minas connected with the department of public works, by the Oficina hidrografica, and more especially in connexion with surveys necessitated by the boundary disputes with Argentina, which were settled by arbitration in 1899 and 1902.