were (as we shall see hereafter) rather "show-ships," and cannot be considered as representing the usual type of even the most sumptuous of ancient merchant vessels.
Nautical instruments. The skilled mariners of ancient days determined their latitude by means still in use, but their instruments were very inferior. The gnomon, in some form or other, was their most common instrument for measuring the length of the sun's shadow at noon on different days and in different places. We know from Herodotus,[1] that this instrument was of great antiquity—indeed, he ascribes the invention of it to the Babylonians; but the report of Arrian to the Emperor Hadrian[2] of his shipwreck implies that there were other instruments besides this on board. Pytheas, the first known navigator of the North Sea, is said to have determined the summer solstice at Marseilles by observing the proportion of the shadow of the gnomon.[3] Further, Eratosthenes drew a parallel of latitude through Gibraltar, Rhodes, and Lycia to India; while Hipparchus made the first map, on the principle of "Mercator's Projection," by transferring the celestial latitudes and longitudes to the terrestrial globe. On the other hand, Ptolemy erred so far in his calculation of the longitude, that he placed China 60° nearer Europe than it really is, and thus led Columbus to fancy the distance he had to traverse to the New World was just so much less. It must not, however, be forgotten that Aristotle,
