The two most famous charts hitherto published, [i.e. in 1745,] of the southern parts of South America, are those of Dr Halley, in his General Chart of the Magnetic Variation, and of Frezier, in his Voyage to the South Seas. Besides these, there is a chart of the Straits of Magellan and some parts of the adjacent coast, by Sir John Narborough, which is doubtless infinitely more exact in that part than Frezier’s, and even in some parts superior to Halley’s, particularly in regard to the longitudes of different places in these straits. We were in some measure capable of correcting, by our own observations, the coast from Cape Blanco to Terra del Fuego, and thence to the Straits of Le Maire, as we ranged along that coast, generally in sight of land. The position of the land to the northward of the Straits of Magellan, on the western side of Patagonia, is doubtless laid down very imperfectly in our charts; and yet I believe it to be much nearer the truth than any hitherto published; as it was drawn from the information of some of the crew of the Wager, which was shipwrecked on that coast; and as it pretty nearly agrees with what I have seen in some Spanish manuscripts. The channel, called Whale Sound, dividing Terra del Fuego, towards the western extremity of the Straits of Magellan, was represented by Frezier; but Sir Francis Drake, who first discovered Cape Horn, and the south-west parts of Terra del Fuego, observed that the whole coast was indented by a great number of inlets, all of which he conceived to communicate with the Straits of Magellan: And I do not doubt, when this country shall be thoroughly examined, that this conjecture will be verified, and that Terra del Fuego will be found to consist of several islands.
I must not omit warning all future navigators against relying on the longitude of the Straits of Le Maire, or of any part of that coast, as laid down by Frezier; the whole being from eight to ten degrees too far to the eastward, if any faith can be given to the concurrent evidences of a great number of journals, verified, in some particulars, by astronomical observations. For instance, Sir John Narborough places Cape Virgin Mary in long. 65 deg. 42’ W. from the Lizard, or about 71 deg. 20’ from London. The ships of our squadron, taking their departure from St Catharines, where the longitude was rectified by an observation of an eclipse of the moon, found Cape Virgin Mary to be from 70 deg. 15’ to 72 deg. 30’ W. from London, according to their different reckonings; and, as there were no circumstances in our run that could Tender it considerably erroneous, it cannot be estimated in less than 71 deg. W. from London; whereas Frezier makes it only 66 deg. W. from Paris, which is little more than 63 deg. from London. Again, our squadron found the difference of longitude between Cape Virgin Mary and the Straits of Le Maire to be not more than 2 deg. 30’, while Frezier makes the difference nearly 4 deg., by which he enlarged the coast, from the Straits of Magellan to the Straits of Le Maire, to near double its real extent.