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 else even in parts then unknown. Curiously enough no reference is made to Alexander's Demarcation Bulls.

The second part of my subject, the determination of the line, was beset with difficulties. The primary difficulty lay in the fact, that if the line ever should be taken to determine disputed boundaries it would have to be located with exactness, and to measure longitude with accuracy was entirely beyond the science of the time.

There were no chronometers; the modern chronometer dates from 1748. Their astronomical tables were very defective, and the very first step, agreement as to length of a degree on a great circle, could not be reached, as the first accurate measurement was not made until 1669. Probably these difficulties did not exist for Pope Alexander.

Humboldt suggested that the Demarcation Line was placed 100 leagues west of the Azores in order that it might coincide with the meridian of magnetic no-variation, whose existence Columbus had discovered on his first voyage. Columbus noted other physical changes 100 leagues west of the Azores. On this hypothesis, it would always have been possible for the mariner to know when he crossed the Demarcation Line. Here would have been a genuine "scientific frontier." Humboldt, Untersuchungen, II, 37. This hypothesis is accepted by Dawson as amounting to a "certainty," p. 493. Harrisse, on the other hand, declares it "scarcely admissible." Diplomatic History, 38. The evidence is against Humboldt and Dawson. Columbus first records the variation of the needle in his journal under date of September 17, when, according to the sum of the distances traversed each day, he had gone at least 350 leagues west of Gomera in the Canaries. As the middle of the Azores lies about five degrees west of Gomera, the spot where the variation of the compass was first noticed would be from 250 to 270 leagues west of the Azores, according to the varying estimates of the length of a degree made by the geographers of the day. The estimates ranged roughly from 16 to 20 leagues to the degree. It was only in the account of his third voyage, 1498, that Columbus says that in his voyage to the Indies he noticed changes in the sea and sky and the variation of the needle one hundred leagues west of the Azores (Navarrete, I, 254). The discrepancy is not strange, perhaps, in view of the lack of means for measuring longitude, but the location of these phenomena—exactly 100 leagues west of the Azores—in 1498 looks a little like an afterthought. Possibly Columbus stretched a point to bring forward evidence in favor of the original line. Again, if the distance of 100 leagues from the Azores was chosen for scientific reasons, why do we hear of no objection to the removal of the line to 370 leagues west of the Cape de Verde Islands, which would sacrifice these scientific advantages? The distance 100 leagues may have occurred to the Pope as a reasonable margin of protection to Portugal, or it may have been adopted from the suggestion of Ferdinand and Isabella. Herrera tells us that the ambassador sent to the Pope in the first instance received the following instructions: "The ambassador was directed to let him know, that the said discovery had been made, without encroaching upon the crown of Portugal, the admiral having been positively commanded by their Highnesses not to come within 100 leagues of the mine, nor of Guinea, or any other part belonging to the Portugueses, which he had done accordingly." Dec. I, Lib. II, ch. iv., John Stevens' version. But the line was moved and thus a dispute