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Instructions ^or the Expedition into Central Africa from the 

 Cape of Good Hope, 2Sd June 1834. 



The " Instructions" drawn up for the guidance of Dr Smith, 

 the chief of the exploratory expedition, at present in the interior 

 of Africa, were sanctioned by Sir WiUiam Herschell, and othe^ 

 distinguished individuals at the Cape of Good Hope, interested 

 in the success of the enterprise. The following pages from the 

 " Instructions'" will be read with advantage by those who may 

 embark in similar journeys. 



• " At primary stations the Committee recommend the assiduous application 

 of every instrumental means for the determination of the three elements of 

 latitude, longitude, and elevation above the level of the sea, and especially 

 at such stations as many series of lunar distances as possible should be pro- 

 cured, in addition to the usual sights for time (or observations of the altitudes 

 of heavenly bodies near the prime vertical) which, together with meridian 

 observations for the latitude, they would recommend to be practised daily as 

 a matter of regular duty, at every station, as well primary as secondary. At 

 primary stations also the barometer and thermometer should be observed at 

 regular intervals, and the magnetic variatioin ascertained by taking the suii^- 

 azimuth immediately before and after the obseruation for time (noting the exact mo- 

 ments, and thtis obtaining data for interpolating to the time of observation). At 

 such stations likewise a careful investigation of the Index errors of Sextants 

 should be made, the zero points or index corrections of the Sympiesometer 

 should be determined by leisurely comparison with the mountain Barometer 

 (giving time for the instruments to attain the same temperature), and the dif- 

 ference noted in the observation-books. The necessity of frequent compari- 

 sons of these instruments will be apparent, if it be considered that in the 

 event of fracture of the barometer tube, no other means will exist by which 

 the zero point of a new one can be determined. Occultations of stars by the 

 moon, and, if possible, eclipses of the satellites of Jupiter, should be observed 

 whenever an opportunity may occur. The former especially, affording the 

 best known method of ascertaining the longitude by a single observation, 

 should be constantly borne in mind, and the Almanac consulted several days 

 in advance, so that no occultation of a large star certainly identifiable, should 

 be allowed to escape through inadvertence. 



" The Committee especially recommend that every observation made should 

 be registered in a book devoted to that purpose, and preserved in the ex'act 

 terms of the readings off of the instruments and chronometers, and kept rigorously 

 separate in its statement from any calculation thereon grounded, and ftiat 

 the observed or presumed index or zero corrections, whether of Chronometer, 

 Sextant, Barometer, or other instrument, should be stated separately in everv 

 case, and on no account incorporated with observed quantities ; and, moreover, 

 that the observations upon which such index errors have been concluded, 



