VOL. LIIl.] PHILOSOPHICAL TRANSACTIONS. 6QQ 



of meridional parts, constructed by the most accurate method, only shows that 

 Mr. Wright's tables do no where exceed the true meridional parts by half a 

 minute, and this only near the pole ; for, in latitudes as far as navigation is 

 practicable, the difference is scarcely sensible." 



About the year 1720, a curvilinear sea chart made its appearance, said to be 

 done by Henry Wilson, the publishers of which represented Wright's chart as 

 puzzling, difficult, and false. But these groundless assertions were rationally 

 answered by Mr. Thomas Haselden, afterwards master of the Royal Academy 

 at Portsmouth, in a letter and pamphlet addressed to Dr. Halley about the 

 year 1722. 



In the year 1755 was published a book intitled, " The art of sailing upon the 

 Sea," by W. E.* which initial letters are sufficient to point out the ingenious 

 author. In page 74, he says, " It is demonstrable, by the method of fluxions, 

 that the length of the part of the meridian line in Mercator's chart, which 

 represents the difference of latitude of two places on the globe, is equal to the 

 difference of the log. tangents of half the complements of the two latitudes, 

 multiplied into the number 2.30258509, and that product into the radius of 

 the sphere." And in the Scholium to his Fundamental principles, page 75. " In 

 the few foregoing propositions, I have demonstrated the truth of the chief 

 methods of sailing now in use ; and deduced them from their genuine princi- 

 ples, and fixed them on their proper foundations : by which the reader will be 

 enabled to see that this theory is not founded on false principles ; but on such 

 as are solid and true ; and consequently that all calculations built on it may be 

 depended on as exact." 



Notwithstanding these, Wright's method is charged with great imperfection 

 by the late Mr. West of Exeter, in his posthumous work, Mr. West therein 

 declares that " the errors of the plain chart are corrected, in a great measure, 

 by Mercator's or Wright's chart ; though the latter is not a true projection of 

 the sphere in any shape ; nor indeed is it pretended to be such by Mr. Wright, 

 one of its inventors." — ^The first part of this paragraph surely contains a contra- 

 diction ; for how can the errors in the plain chart be in a great measure cor- 

 rected by a projection that is not true in any shape ? And in answer to the 

 latter part, — Mr. Wright has no where made such concessions. And further, 

 Mr. West blends Wright and Mercator together, when at the same time it 

 does not appear that the latter ever published any principles of this kind of 

 projection to the world. 



In the 20th article of the book, Mr. West has laid down a method of con- 

 structing a nautical chart, which he asserts to be " the first representation of 



* William Emerson. 

 4 V 2 



