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XLIII. Principles offnding the Longitude, By A Corre- 

 spondent. 



To Mr. Tilloch. 



Sir, — After all the labour which has been bestowed to ren- 

 der the present practice of ascertaining the longitude worthy of 

 general estimation, to institute another method by which the 

 complete solution of that problem can be attained, may seem un- 

 vrarrantably bold ; but, while the author's conviction of its truth 

 has urged him to seek for an opportunity of making it public, a 

 consciousness of his attainments being very limited in comparison 

 with the great acquirements of those who have already pursued 

 this interesting investigation, compels him to acknowledge that 

 to a fortuitous thought rather than to an extensive acquaintance 

 with science, are to be ascribed the researches which he thus 

 ventures to present. 



That his suggestions may be candidly criticized, and any theo- 

 retical errors or impracticable proposals pointed out by those 

 more conversant with astronomical pursuits, he requests with re- 

 spectful deference. 



Definition of the Subject. 



To discover the longitude of any place is to find out what me- 

 ridian passes through it, and to calculate how far that and the 

 first meridian are apart. And this should be done by a process 

 as simple as the case allows, one that is often at command, and 

 which can be performed with a requisite dispatch to the certainty 

 of the operation. 



From the nature of the question, the means by which it is de- 

 terminable must have relation to the first meridian. 



Now, the relation which subsists between the fixed stars and 

 the first meridian is direct and constant ; for once in every re- 

 volution of the earth, the same stars are vertical to the same 

 places on its surface ; and not only does the earth fulfil every re- 

 volution on its axis in the same time, but also revolves with an 

 equal)le motion throughout : whereas its motion in the annual 

 revolution varies as the progress from equinox to equinox. 



Hence, every star will describe equal arcs of its circle of ap- 

 parent revolution in equal times ; and any arc of a star's circle 

 of revolution will be to the time in which the star describes that 

 arc, proportionately as the whole circle, or iJOO degrees, is to the 

 time in which the star complete.'? a revolution. 



Again : the torraciucous globe and the apparent orb of the fixed 

 stars°are concentric ; and they may l)e said to revolve in regard 

 of each other conversely; so" that' if a meridian of each sphere 



coincide 



