22 THE MONTHLY
V A R I E T I E S
W O N D E R S O F S C I E N C E
Anecdote of Capt. Basil Hall.
THAT a man, by merely measuring the moon's apparent distance from a star, with a little portable instrument held in his hand, and applied to his eye, even with so unstable a footing as the deck of a ship, shall say positively, within five miles, where he is, on a boundless ocean, cannot but appear to persons ignorant of astronomy an approach to the miraculous. Yet the alternatives of life and death, wealth and ruin, are daily and hourly staked with perfect confidence on these marvelous computations. We have before us an anecdote communicated to us by a naval officer (Captain Basil Hall, R. N.) distinguished for the extent and variety of his attainments, which shows how impressive such results may become in practice. He sailed from San Blas, on the west coast of Mexico, and after a voyage of 8000 miles, occupyiug 89 days, arrived off Rio de Janeiro, having, in this interval, passed through the Pacific Ocean, rounded Cape Horn, and crossed the South Atlantic, without making any land, or even seeing a single sail, with the exception of an American whaler off Cape Horn. Arrived within a week's sail of Rio, he set seriously about determining, by lunar observations, the precise line of the ship's course, and its situation in it at a determinate moment, and having ascertained this, within from five to ten miles, ran the rest of the way by those more ready and compendious methods, known to navigators, which can be safely employed for short trips between one known point and another, but which cannot be trusted in long voyages, where the moon is the only sure guide. The rest of the tale we are enabled by his kindness to state in his own words:-- We steered to- wards Rio de Janeiro for some days after taking the lunars above de- scribed, and having arrived within fifteen or twenty miles of the coast, I hove to at four in the morning till the day should break, and then bore up; for although it was very hazy, we could see before us a couple of miles or so. About eight o'clock it became so foggy that I did not like to stand in further, and was just bringing the ship to the wind a- gain before sending the people to breakfast, when it suddenly cleared off, and I had the satisfaction of seeing the great Sugar Loaf Rock, which stands on one side of the harbour's mouth, so nearly right a-head that we had not to alter our course above a point in order to hit the en- trance of Rio. This was the first land we had seen for three months after crossing so many seas and being set backwards and forewards by innumerable currents and foul winds." The effect on all on board might well be conceived to have been electric; and it is needless to re- mark how essentially the authority of a commanding officer over his crew may be strengthened by the occurrence of such incidents, indica- tive of a degree of knowledge and consequent power beyond their reach.