Narrative of the surveying voyages of his majesty's ships Adventure and Beagle (vol.2): between the years 1826 and 1836 : describing their examination of the southern shores of South America, and the Beagles's circumnavigation of the globe

GENERAL IIEMAIIKS. 37 interesting to astronomers, and if it would not much derange her operations, she should be taken to some convenient ancho- rage for the purpose of landing the instruments. " If a comet should be discovered while the Beagle is in port, its position should be determined every night by observ- ing its transit over the meridian, always accompanied by the transits of the nearest known stars, and by circum-meridional altitudes, or by measuring its angular distance from three well- situated stars by a sextant. This latter process can be effected even at sea, and the mean of several observations may give veiy near approximations to its real position. " Meteorological Registers may be of use in a vai-iety of ways ; but then they must be steadily and accurately kept. The barometer should be read off to the third place of decimals, and recorded at regular periods of the day ; nine o''clock and four o'clock may be recommended as the best, as being the usual hours of its maximum and minimum. The temperature should be marked at the same time, and the extremes of the self-registering thermometer should be daily recorded; care being taken that no reflected heat should act on any of these instruments. The temperature of the sea at the surface ought to be frequently observed and compared with that of the air. An officer cruizing on the east coast of South America, be- tween the pai-allels of 20° and 35°, was enabled by these means to predict with singular precision the direction and strength of the current. " In this register the state of the wind and weather will, of course, be inserted ; but some intelligible scale should be assumed, to indicate the force of the former, instead of the ambiguous terms ' fresh,' ' moderate,' &c., in using which no two people agree ; and some concise method should also be employed for expressing the state of the weather. The sugges- tions contained in the annexed printed paper are recommended for the above purposes, and if adopted, a copy should be pasted on the first page of every volume of the log-book ; and the officer of the watch should be directed to use the same terms in the columns of the log-board.