S52 Captain HalPs Notice of a Voyage of Research. 



utility in the practice of Navigation, and the advance- 

 ment of Geographical Science. 



Secondly, To institute experiments, and series of obser- 

 vations, calculated to improve the Theory of Naviga- 

 tion, by furnishing mathematicians with data for the 

 coiTection of Nautical and Astronomical Tables. 



Thirdly, To ascertain the, resources, Nautical and Commer- 

 cial, of remote countries. 



Fourthly, To make observations of a scientific nature, in 

 places distant from England, and under circumstances 

 of situation and climate which are not to be obtained at 

 home ; and which, independently of their own local va- 

 lue, would in many cases enhance the importance and 

 utility of observations already made ; while, at the 

 same time, the field of new knowledge would be ex- 

 tended and enclosed, if I may use such an expression, 

 and that of prejudice and error contracted. 



Fifthly, To attend to that class of topics called Popular, 

 having less in view any precise object of utility, than 

 the rational amusement and information of persons who 

 have no means of investigating such subjects for them- 

 selves. 



The desideratum which is unquestionably of most importance 

 in practical navigation, is the exact measurement of the Diffe- 

 rence of longitude between place and place, especially between 

 those headlands and harbours generally used as points of depar- 

 ture by ships starting, or which are looked out for as land-marks 

 on their return voyage. It is not necessary this should be done 

 with that rigorous precision used in trigonometrical surveys. 

 The well-being of navigation, however, certainly requires that 

 this element should be determined within much smaller limits 

 than those which at present bound our information. Without 

 such knowledge, indeed, much of the utility of improving nau- 

 tical instruments and tables is essentially lost. It may assist 

 your imagination to consider, that the evil of loosely settled 

 longitudes, is quite as great in practice, as if the geographical 

 positions of the places on the earth'*s surface were supposed 

 to be actually shifted about from time to time. No skill, it must 



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