Ptolemy's opinion as to the length of the Inhabited World was considerably modified in the minds of those writers who toward the end of the Middle Ages had been strongly impressed by the book of Marco Polo. Among these persons was Toscanelli. Toscanelli's calculation of the size of the earth, This excellent astronomer calculated the earth's equatorial circumference at almost exactly the true figure; his error was less than 124 English miles in excess. The circumference in the latitude of Lisbon he made 26 × 250 × 3 = 19,500 miles.[461] Two thirds of this figure, or 13,000 miles, he allowed for the length of the Œcumene, from Lisbon eastward to Quinsay (i. e. Hang-chow), leaving 6,500 for the westward voyage from Lisbon to Quinsay. Thus Toscanelli elongated Asia by nearly the whole width of the Pacific ocean. His Quinsay would come about 130° W., a few hundred miles west of the mouth of the Columbia river. Zaiton (i. e. Chang-chow), the easternmost city in Toscanelli's China, would come not far from the tip end of Lower California. Thus the eastern coast of and of the position of Cipango. Cipango, about a thousand miles east from Zaiton, would fall in the Gulf of Mexico somewhere near the ninety-third meridian, and that island, being over a thousand miles in length north and south, would fill up the space between the parallel of New Orleans and that of the city of Guatemala. The westward voyage from the Canaries to Cipango, according to Toscanelli, would be rather more than 3,250 miles, but at a third of the distance out he placed the imaginary island of "Antilia," with which he seems to have supposed Portuguese sailors to be familiar.[462] "So through the unknown parts of the route," said the venerable astronomer, "the stretches of sea to be traversed are not great,"—not much more than 2,000 English miles, not so long as the voyage from Lisbon to the Guinea coast.
While Columbus attached great importance to these calculations and carried Toscanelli's map with him upon his first voyage, he improved somewhat upon the estimates of distance, and thus made his case still more hopeful. Columbus's opinion of the size of the globe, the length of the Œcumene, and the width of the Atlantic ocean. Columbus was not enough of an astronomer to adopt Toscanelli's improved measurement of the size of the earth. He accepted Ptolemy's figure of 20,400 geographical miles for the equatorial girth,[463] which would make the circumference in the latitude of the Canaries about 18,000; and Columbus, on the strength of sundry passages from ancient authors which he found in Alliacus (cribbed from Roger Bacon), concluded that six sevenths of this circumference must be occupied by the Œcumene, including Cipango, so that in order to reach that wonderful island he would only have to sail over one seventh, or not much more than 2,500 miles from the Canaries.[464] An authority upon which he placed great reliance in this connection was the fourth book of The fourth book of Esdras. Esdras, which although not a canonical part of the Bible was approved by holy men, and which expressly asserted that six parts of the earth (i. e. of the length of the Œcumene, or north temperate zone) are inhabited and only the seventh part covered with water. From the general habit of Columbus's mind it may be inferred that it was chiefly upon this scriptural authority that he based his confident expectation of finding land soon after accomplishing seven hundred leagues from the Canaries. Was it not as good as written in the Bible that land was to be found there?
Thus did Columbus arrive at his decisive conclusion, estimating the distance across the Sea of Darkness to Japan at something less than the figure which actually expresses the distance to the West Indies. Many a hopeful enterprise has been ruined by errors in figuring, but this wrong calculation was certainly a great help to Columbus. Fortunate mixture of truth and error. When we consider how difficult he found it to obtain men and ships for a voyage supposed to be not more than 2,500 miles in this new and untried direction, we must admit that his chances would have been poor indeed if he had proposed to sail westward on the Sea of Darkness for nearly 12,000 miles, the real distance from the Canaries to Japan. It was a case where the littleness of the knowledge was not a dangerous but a helpful thing. If instead of the somewhat faulty astronomy of Ptolemy and the very hazy notions prevalent about "the Indies," the correct astronomy of Toscanelli had prevailed and had been joined to an accurate knowledge of eastern Asia, Columbus would surely never have conceived his great scheme, and the discovery of America would probably have waited to be made by accident.[465] The whole point and purport of Columbus's scheme. The whole point of his scheme lay in its promise of a shorter route to the Indies than that which the Portuguese were seeking by way of Guinea. Unless it was probable that it could furnish such a shorter route, there was no reason for such an extraordinary enterprise.
The years between 1474 and 1480 were not favourable for new maritime ventures on the part of the Portuguese government. The war with Castile absorbed the energies of Alfonso V. as well as his money, and he was badly beaten into the bargain. About this time Columbus was writing a treatise on "the five habitable zones," intended to refute the Columbus's speculations on climate. old notions about regions so fiery or so frozen as to be inaccessible to man. As this book is lost we know little or nothing of its views and speculations, but it appears that in writing it Columbus utilized sundry observations made by himself in long voyages into the torrid and arctic zones. His voyage to Guinea. He spent some time at the fortress of San Jorge de la Mina, on the Gold Coast, and made a study of that equinoctial climate.[466] This could not have been earlier than 1482, the year in which the fortress was built. Five years before this he seems to have gone far in the opposite direction. In a fragment of a letter or diary, preserved by his son and by Las Casas, His voyage into the Arctic ocean, 1477. he says:—"In the month of February, 1477, I sailed a hundred leagues beyond the island of Thule, [to?] an island of which the south part is in latitude 73°, not 63°, as some say; and it [i. e. Thule] does not lie within Ptolemy's western boundary, but much farther west. And to this island, which is as big as England, the English go with their wares, especially from Bristol. When I was there the sea was not frozen. In some places the tide rose and fell twenty-six fathoms. It is true that the Thule mentioned by Ptolemy lies where he says it does, and this by the moderns is called Frislanda."[467]
Taken as it stands this passage is so bewildering that we can hardly suppose it to have come in just this shape from the pen of Columbus. It looks as if it had been abridged from some diary of his by some person unfamiliar with the Arctic seas; and I have ventured to insert in brackets a little preposition which may perhaps help to straighten out the meaning. By Thule Columbus doubtless means Iceland, which lies between latitudes 64° and 67°, and it looks as if he meant to say that he ran beyond it as far as the little island, just a hundred leagues from Iceland and in He may have reached Jan Mayen island, latitude 71°, since discovered by Jan Mayen in 1611. The rest of the paragraph is more intelligible. It is true that Iceland lies thirty degrees farther west than Ptolemy placed Thule; and that for a century before the discovery of the Newfoundland fisheries the English did much fishing in the waters about Iceland, and carried wares thither, especially from Bristol.[468] There can be no doubt that by Frislanda Columbus means the Færoe and stopped at Iceland. islands,[469] which do lie in the latitude though not in the longitude mentioned by Ptolemy. As for the voyage into the Jan Mayen waters in February, it would be dangerous but by no means impossible.[470] In another letter Columbus mentions visiting England, apparently in connection with this voyage,[471] and it is highly probable that he went in an English ship from Bristol.
The object of Columbus in making these long voyages to the equator and into the polar circle was, as he tells us, to gather observations upon climate. From the circumstance of his having made a stop at some point in Iceland, it was conjectured by Finn Magnusson The hypothesis that Columbus "must have" heard and understood the story of the Vinland voyages. that Columbus might have learned something about Vinland which served to guide him to his own enterprise or to encourage him in it. Starting from this suggestion, it has been argued[472] that Columbus must have read the geographical appendix to Adam of Bremen's "Ecclesiastical History;" that he must have understood, as we now do, the reference therein made to Vinland; that he made his voyage to Iceland in order to obtain further information; that he there not only heard about Vinland and other localities mentioned in the sagas, but also mentally placed them about where they were placed in 1837 by Professor Rafn; that, among other things, he thus obtained a correct knowledge of the width of the Atlantic ocean in latitude 28° N.; and that during fifteen subsequent years of weary endeavour to obtain ships and men for his westward voyage, he sedulously refrained from using the most convincing argument at his command,—namely that land of continental dimensions had actually been found (though by a very different route) in the direction which he indicated.
I have already given an explanation of the process by which Columbus arrived at the firm belief that by sailing not more than about 2,500 geographical miles due west from the Canaries he should reach the coast of Japan. Every step of that explanation is sustained by documentary evidence, and as his belief is thus completely accounted for, the hypothesis that he may have based it upon information obtained in Iceland is, to say the least, superfluous. We do not need it in order to explain his actions, and accordingly his actions do not afford a presumption in favour of it. That hypothesis has no evidence in its favour. There is otherwise no reason, of course, for refusing to admit that he might have obtained information in Iceland, were there any evidence that he did. But not a scrap of such evidence has ever been produced. Every step in the Scandinavian hypothesis is a pure assumption.
First it is assumed that Columbus must have read the appendix to Adam of Bremen's history. But really, while it is not impossible that he should have read that It is not probable that Columbus knew of Adam of Bremen's allusion to Vinland, document, it is, on the whole, improbable. The appendix was first printed in Lindenbrog's edition, published at Leyden, in 1595. The eminent Norwegian historian, Gustav Storm, finds that in the sixteenth century just six MSS. of Adam's works can now be traced. Of these, two were preserved in Denmark, two in Hamburg, one had perhaps already wandered southward to Leyden, and one as far as or that he would have understood it if he had read it. Vienna. Dr. Storm, therefore, feels sure that Columbus never saw Adam's mention of Vinland, and pithily adds that "had Columbus known it, it would not have been able to show him the way to the West Indies, but perhaps to the North Pole."[473] From the account of this mention and its context, which I have already given,[474] it is in the highest degree improbable that if Columbus had read the passage he could have understood it as bearing upon his own problem. There is, therefore, no ground for the assumption that Columbus went to Iceland in order to make inquiries about Vinland.