Such is the minimising view; and most, in face of this sharp divergence, will agree with Baron Nordenskjöld that a really critical study of the subject, especially from a local antiquarian, is desirable. Very plausibly does Nordenskjöld himself sum up the probabilities of the case when he concludes that "a small school of navigation, important for the period in question, has probably received from laudatory biographers the name of an 'Academy.'"[223] The Swedish geographer, however, adds from his own special researches some important observations. He believes that in the La Cosa map of 1500[224] we have work which was based upon the observations of the Infant's captains, who, as shown in these results, were evidently able to keep reliable reckoning and take fairly correct altitudes. "Further, the extension of the normal or typical portolano along the West coast of Africa, as on the portolanos of Benincasa and others of the latter part of the fifteenth century, is shown by the legends of the same to have been based on observations made during the marine expeditions of Prince Henry." [Footnote 223: Nordenskjöld, _Periplus_, 121 A.] [Footnote 224: Plates xliii and xliv of Nordenskjöld's _Periplus_.] No charts or other productions of the "Sagres School," in any definite sense of this term, no geographical or astronomical works emanating from the "Court" of the Infant, are now extant. But it may reasonably be inferred from passages in Azurara's _Chronicle of Guinea_ that such charts were not only draughted under the Prince's orders, but used by his sailors;[225] Cadamosto tells us of the chart he kept on his voyage of 1455, probably by direction of the Infant; while it is probably true that the "extension of the portolanos beyond Cape Bojador, in Benincasa,[226] for instance, as well as in Fra Mauro's work of 1457-9, depended on information given by native and foreign skippers" sent out by Henry. Of course, it is obvious, in the light of present knowledge, that neither he nor his school in any sense invented the portolano type; although the mention of Master Jacome of Majorca reminds us of one of the earliest centres of the new scientific cartography[227] (which was probably first made effective by Catalan skippers and draughtsmen), and suggests that the Infant was in touch with the best map-science of the time. "Neither is it correct to say that he introduced hydrographic plane charts or map graduation in accordance with geographical co-ordinates." [Footnote 225: See Azurara, _Guinea_, ch. lxxviii; Nordenskjöld, _Periplus_, 121; Santarem, _Essai sur Cosmographie_, vol. iii, p. lix. Affonso Cerveira, Azurara's predecessor, was probably not a "pupil" of the "Sagres School," as some have supposed.] [Footnote 226: Especially in his works of 1467-8 and 1471.] [Footnote 227: In the Balearic isles. See pp. cxvii-cxix of this Introduction.]