many acts of friendship, we weighed on the morning of the ninth, after sending our letters and despatches on board the "Bombay" for conveyance to England, and proceeded on our voyage.
The trade wind prevented our fetching so far to the eastward as I wished, so that Ave crossed for a third time the line of least magnetic intensity in lat. 21° S. and long. 8° W. Our slow progress through this, magnetically speaking, very interesting region afforded us the opportunity of obtaining a vast number of observations, which having been transmitted to England from the Cape of Good Hope were placed in the hands of Lieut. Colonel Sabine of the Royal Artillery, and published, under his supervision, in the Philosophical Transactions[1] of the Royal Society, to which I must refer the scientific inquirer for the observations themselves, and also for a more detailed account of the results. It is enough to state here, in the words of Col. Sabine, "that the determination of the position of the line of least intensity is easier, and in some respects more sure, than that of an isodynamic line, because it is independent of the correctness of an assumed intensity at a base station. It is therefore to be expected that the position of this line will become in future years the subject of frequent examination, seeming to mark, from time to time, the progress of the secular change in its position. This may be done with the more interest and ad-
