A Manuscript Atlas by Battista Agnese in the Society's Collection

Abstract

Among the atlases presented to the Society by the Trustees of Mrs. Henry Yates Thompson is a magnificent example of a manuscript portolan atlas, which, though unsigned, may confidently be ascribed to Battista Agnese, and dated approximately 1550. It is briefly described by Mr. Henry Yates Thompson in his 'Descriptive catalogue of the second series of fifty manuscripts . . .,' Cambridge, 1902. Before discussing it in detail, it may be useful'to indicate briefly the development of these atlases, and the relation of Agnese's work to it. The earliest known portolan charts date from the early years of the four? teenth century, though it is clear, from incidental references, that they were in existence in the preceding half-century at least. Early in their history they assumed certain definite characteristics, which the class known as normal portolans preserved with few changes throughout. Their main features are: they cover in general an area from the Black Sea to the western coast of Europe and North Africa, extending on the north to the Baltic, which is frequently included; the coastline, though faintly drawn, is emphasized by the closely packed series of names, the majority in black with important places in red; they provide a special method of ascertaining direction. The earliest charts are covered by numerous lines which radiate from two or more points, generally thirty-two lines from each. The next stage is the combination of these lines with indications of the cardinal points, as on the Angellino de Dolorto chart of c. 1325. A compass rose appears for the first time on the Catalan world chart of 1375, and the fully developed symetrical arrangement of com? pass roses and direction lines is a late development in the charts. By selecting a direction line parallel to his proposed course between two points, the pilot could read from the compass rose the direction he required to follow. (Mag? netic variation is not indicated.) Whether the evolution of the portolan chart was dependent upon the introduction of the mariner's compass has been much debated. Their content probably embodied material from the written directions or peripli, which were in use from Roman times, and the earlier charts were put together from sectional charts of the coasts. The construction of the earliest known chart, the so-called Carte Pisane, strongly suggests this. No doubt in assembling these sections, use was made of compass bearings. The charts have no meridians or parallels; so long as they were confined to the Mediterranean area, the problem of the sphericity of the earth raised no diffi? culties. As Nordenskiold has shown, the resulting outline was remarkably accurate.

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